DRAFT. Future neutrino oscillation facilities: physics priorities and open issues. Alain Blondel

Transcription

1 DRAFT Futur nutrino oscillation facilitis: physics prioritis and opn issus Alain Blondl DPNC Sction d Physiqu 24 quai Ansrmt Univrsity of Gnva CH 1211 Gnèv 23 Switzrland Invitd prsntation at NUFACT05, Frascati, Jun 2005 Abstract: Th rcnt discovry that nutrinos hav masss opns a wid nw fild of xprimntation, for which on has to b ambitious, ingnious and patint. Acclrator-mad nutrinos ar ssntial in this program. Idas for futur facilitis includ high intnsity muon nutrino bams from pion dcay ( Suprbam ), lctron nutirno bams from nucli dcays ( Bta-bam ), or muon and lctron nutrino bams from muon dcay ( Nutrino Factory ), ach associatd with on or svral options for dtctor systms. Thr ar diffrnt opinions in th community on how to procd through this rich choic of qustions and possibilitis. W now bgin a scoping study aimd at dtrmining a st of ky R&D projcts nabling th community to propos an ambitious acclrator nutrino program at th turn of this dcad. As an introduction to this study, a st of physics prioritis, a summary of th prcivd virtus and shortcomings of th various options, and a numbr of opn qustions ar prsntd. 1

2 1 Introduction 1.1 Status of th fild Th obsrvation of nutrino oscillations has now stablishd byond doubt that nutrinos hav mass and mix. This xistnc of nutrino masss is in fact th first solid xprimntal fact rquiring physics byond th Standard Modl. Th prsnt status of th fild is as follows. Sinc 1989, w know from LEP [LEPEW] that thr ar only thr familis of activ light nutrinos coupling to th wak intraction. Sinc th arly 1970 s w hav hints from solar nutrino xprimnts that lctron nutrinos producd in th sun undrgo disapparanc on thir way to arth, and, from th diffrnt disapparanc rats for xprimnts snsitiv to diffrnt nutrino nrgy rangs (Gallium, Chlorin, Watr Chrnkov) w hav indication that mattr ffcts in th sun play an important rol. This solar nutrino puzzl was closd in 2002 with th rsults from th SNO xprimnt, which allowd simultanaously i) a dirct masurmnt of th total flux of activ nutrinos by th nutral currnt raction in agrmnt with solar nutrino flux calculations, and ii) a masurmnt of th lctron nutrino componnt, by th chargd currnt raction, dtrmining that thy rprsnt lss than half of th total flux, in agrmnt with prvious obsrvations. Th Kamland xprimnt providd at th sam tim a masurmnt of disapparanc of lctron anti-nutrinos from nuclar fission ractors in Japan, providing, in combination with th solar nutrino rsults, a prcis dtrmination of th rlvant nutrino mixing angl of around 30 0 and of th corrsponding mass diffrnc -- that can b xprssd as an oscillation quartr-wavlngth of L/E ~15000 km/gv. Sinc th lat 80 s thr has bn indication from atmosphric nutrino xprmnts that th muon nutrinos undrgo disapparanc whn going through th arth; this was finally unambiguously dmonstratd by th SuprKamiokaNDE xprimnt in This disapparanc taks plac at a much shortr quartrwavlngth than for solar nutrinos (L/E~500km/GV); it is not sn for lctron nutrinos, a fact that has bn bst stablishd by th CHOOZ ractor xprimnt. This disapparanc has bn confirmd by th K2K xprimnt in Japan, th first acclrator nutrino long baslin xprimnt dsignd sinc nutrino masss hav bn stablishd, and a prototyp for futur ons. Th abov xprimntal obsrvations ar consistntly dscribd by thr family oscillations, with mass ignstats { 1, 2, 3 } rlatd to th flavour ignstats {,, τ } by a st of Eulr angls θ 12, θ 13, θ 23 as dpictd in Figur 1. Two indpndnt mass splittings charactriz th systm, sinc oscillations only dpnd on th diffrnc of squard masss. Although no formally agrd dfinition xists, th usag is that th mass ignstats ar classifid by dcrasing lctron-nutrino contnt < 1 > 2 > < 2 > 2 > < 3 > 2. (I would propos to mak this a dfinition). With this dfinition, th mass of 1 is not ncssarily smallr than that of 2. Sinc nutrino oscillations in vacuum dpnd on th mass diffrnc as sin 2 (1.27 m 2 L/E) on cannot dtrmin th sign of m 2 unlss th oscillation intrfrs with anothr procss; in th cas of lctron nutrinos, this is offrd by cohrnt scattring on lctrons in mattr, a.k.a. mattr ffcts. Th fact that solar nutrinos undrgo mattr ffcts in th sun allows us to know that m 2 12 δm m m 2 1 >0. Sinc atmosphric nutrino disapparanc has only bn obsrvd for muon nutrinos, which coupl wakly to lctron nutrinos at th rlvant wavlngth, w cannot (yt) tll th sign of th mass diffrnc m 2 13, or m 2 23, or m 2 ( m m 2 23 )/2 as suggstd by Lisi [Lisi]. Th prsnt valus of oscillation paramtrs ar summarizd in Tabl 1 and Figur 1. 2

3 Tabl 1 Nutrino oscillation paramtrs as of NUFACT05 [Lisi] 1 'solar paramtrs' δ m = ± ( 7.92 ± 0.72) 10 V sin 2 θ 12 = atmosphric paramtrs solar-atmosphric transition paramtrs absolut mass m 2 = ± ( )10 V m 2.2 V (tritium dcay) Σm O (1 V) (cosmology) sin 2 θ 23 = sin 2 θ 13 < % C.L. δ unknown Figur 1 Prsnt knowldg of th nutrino mixing matrix. Th bst valus ar, for th angls, θ 12 =32 0, θ 23 = 45 0, θ 13 < 13 0, and for th masss m 2 12 = V 2, m 2 23 = ± 2.5 V 2. Th phas δ gnrats CP and T violation in nutrino oscillations. Bfor laving this sction on th status of th fild, it is worth rmmbring th possibl obsrvation of a apparanc in th proton dump xprimnt at Los Alamos in th LSND xprimnt. This puzzling obsrvation will b soon vrifid of falsifid by th LSND xprimnt at Frmilab. If it is tru this will lad to vn mor xciting phnomnology! 1.2 Thr family oscillations and CP or T violation It was soon ralizd that with thr familis and for a favourabl st of paramtrs, it would b possibl to obsrv violation of CP or T symmtris in nutrino oscillations [Ruj99]. This obsrvation rinforcd th considrabl intrst for prcision masurmnts of nutrino oscillation paramtrs. W know sinc 2002 and th rsults from SNO [SNO02] and KAMLAND [Kamland02] that th nutrino paramtrs blong to th so-calld LMA solution which suggsts that lptonic CP violation should b larg nough to b obsrvd in high-nrgy nutrino oscillation apparanc xprimnts. This has ld to xtnsiv studis, 1 Lisi givs rrors as factors and as 95% C.L. ( 2 sigma ). I hav takn th librty to xprss ths in a mor convntional mannr. 3

4 such as thos publishd rcntly in th CERN yllow rport[ecfarport], or in a rcnt BENE [BENE] workshop on physics at a high intnsity proton drivr [MMW]. Th phnomnon of CP (ot T) violation in nutrino oscillations manifsts itslf by a diffrnc in th oscillation probabilitis of say, P( ) vs P( ) (CP violation), or P( ) vs P( ) (tim rvrsal volation). It can b obsrvd right away that obsrvation of this important phnomnon rquirs apparanc xprimnts; indd a ractor or solar nutrino xprimnt, snsitiv to th disapparanc P( ) which is clarly tim-rvrsal invariant, would b compltly insnsitiv to it. This can b sn as an advantag in viw of a prcis an inambiguous masurmnt of th mixing angls; for th long trm goal of obsrving and studying CP violation, w ar confind to apparanc xprimnts. Th transition can b xprssd as Figur 2: complt formula for th transition; c 12 stands for cos θ 12, tc and ħc=1. Figur 3 Dscription of nutirno oscillations for 1 GV nutrinos as a function of distanc to th sourc. Th oscillation paramtrs ar as in Tabl 1, with : sin 2 2θ 13 = 0.01, δ= 0 for th lft plot, δ= π/2 for th on on th right. On of th intrsting aspcts of this formula is th occurrnc of mattr ffcts which, unlik th straightforward θ 13 trm, dpnd on th sign of th mass diffrnc m Ths trms should allow xtraction of th mass hirarchy, but could also b sn as a background to th CP violating ffct, from which thy can b distinguishd by th vry diffrrnt nutrino nrgy dpndnc, mattr ffcts bing largr for highr nrgis, with a mattr rsonanc at about 12 GV. Th CP violation can b sn as intrfrnc btwn th solar and atmosphric oscillation for th sam transition, as mphasizd in Figur 3. Of xprimntal intrst is th CP-violating asymmtry A CP : 4

5 A CP P( = P( ) P( ) + P( 2 ) sinδ sin ( m12 L/4E) sinϑ ) sinϑ + solar trm or th quivalnt tim rvrsal asymmtry A T which is displayd on Figur 4. Figur 4 Magnitud of th tim rvrsal asymmtry at th first oscillation maximum, for δ=1 as a function of th mixing angl sin 2 2θ 13. Th curv markd rror indicats th θ 13 dpndnc of th statistical rror on such a masurmnt for a givn flux and dtctor mass. Th asymmtry can b larg and its valu incrass for smallr valus of θ 13 up to th valu whn th two oscillations (solar and atmosphric) ar of th sam magnitud. Th following rmarks can b mad: 1. Th ratio of th asymmtry to th statistical rror is fairly indpndnt on θ 13 for larg valus of this paramtr, which xplains th rlativ flatnss of th snsity curvs. 2. This asymmtry is valid for th frst maximum. At th scond oscillation maximum th curv is shiftd to highr valus of θ 13 so that it could b thn an intrsting possibility for masuring th CP asymmtry, although th rduction in flux is considrabl. 3. Th asymmtry has opposit sign for and τ, and changs sign whn going from on oscillation maximum to th nxt. 4. Th asymmtry is small for larg valus of θ 13, placing a challnging mphasis on systmatics in th cross-sction masurmnts. This last point dssrvs a ddicatd discussion. As will b sn latr, facilitis advocatd for larg valus of q13 ar suprbams and bta-bams of rlativly low nrgy aiming at a dtctor mad of watr or scintillator, typically. If th initial bam consists purly of ithr lctron nutrinos or antinutrinos, as is th cas for th bta-bam, of (almost) purly of muon nutrinos and anti-nutrinos, as is th cas for a suprbam, it will b difficult in practic to masur prcisly th oscillation probability, P( ) or 5

6 P( ), by lack of a prcis knowldg of th cross-sction for th final stat nutrino which is absnt in th initial bam and cannot b masurd in th nar dtctor. Although som of th rlatd rrors can prhaps b rducd in th comparison btwn nutrinos and antinutrinos, this difficulty could strongly advocat for a facility which combins both typs of nutrinos, i.. th bta-bam+suprbam combination, or th nutrino factory. 1.3 Stratgy and considrd facilitis In ordr to dsign a facility it is important to dlinat th main physics objctiv that will driv th choic of paramtrs, whil kping in mind othr important physics outcoms and intrsting by-products, that will constitut intrsting slling points of th facility. Of cours such a hirarchy of physics rlvanc is a mattr of choic and is somwhat subjctiv. A common viw nds to b accptd by th community. I hav to confss th following pattrn of mind: 1. Main objctiv: Obsrv and study CP and T violation, dtrmin mass hirarchy. This can b don providd nutrino oscillation probabilitis ar masurd with grat prcision, in an apparanc channl involving lctrons, and ovr a broad rang of nrgis to dcifr th mattr ffct from th CP violation. 2. Important objctivs: unambiguous prcision masurmnts of mixing angls and mass diffrncs. 3. by-products: prcision short baslin nutrino physics, unitarity tsts, nuclar physics, muon collidr prparation, muon EDM. 4. Othr physics capabilitis: nuclon dcay, obsrvation of cosmic vnts (suprnova, cosmic ray bursts, tc..), othr particl physics (muon lpton flavour violating dcays) can w mak on facility that will do all of this? or do w prfr an approach whr ths pics will b producd on at a tim by individual ddicatd xprimnts? Lt m tak hr a purly Europan point of viw, and quot th conclusions of th SPSC workshop in Villars, Futur nutrino facilitis offr grat promis for fundamntal discovris (such as lptonic CP violation) in nutrino physics and a post LHC funding window may xist for a facility to b sitd at CERN. An ambitious nutrino programm is a thus a distinct possibility, but it must b wll prpard to hav a good proposal in tim for th big dcision priod around 2010, whn, LHC rsults bing availabl, th futur of particl physics will b dcidd to a larg xtnt. What can w xpct th situation to b in 2010 as far as th nutrino oscillation businss is concrnd? In Figur 5, th volution of th world combind snsitivity to θ 13 is shown as a function of th yar. It is clar that by that tim our knowldg will hav improvd by almost on ordr of magnitud. In as much as it could b argud that th final dsign of a futur facitily should await bttr knowldg off this paramtr, it is clar that by th nd of th currnt dcad (nd 2010), w will know whthr sin 2 2 θ 13 is largr or smallr than 1%, and that w should b abl by thn to propos a facility accordingly. 6

7 Figur 5 Snsitivity to sin 2 2θ 13 as function of yar taking into account prsntly approvd projcts. Th facilitis that hav bn considrd promising for obsrvation of CP violation ar as follows 1. Suprbam alon + larg dtctor(s) (.g. T2HK, NOvA) 2. SuprBam + Bta-Bam + Mgaton dtctor (SB+BB+MD) Fréjus 3. Nutrino Factory (NuFact) + magntic dtctor (40kton) Th physics abilitis of th nutrino factory hav bn advocatd to b suprior, but th qustion in vryon s mind is «what is th ralistic tim scal?». To a larg xtnt th qustion of tim scal should b dcidd by th cost of th considrd facility. Th (Hardwar) cost stimat for a nutrino factory was stimatd in [StudyIIa] to b ~1B + dtctors, with rathr larg uncrtaintis sinc th original cost stimat was basd on a somwhat diffrnt dsign [studyii]. This stimat nds to b vrifd and ascrtaind on a localizd scnario (CERN, RAL ) and accounting. Th cost of a (BB+SB+MD) is not vry diffrnt A larg cost drivr hr (or in th T2HK option) is th vry larg dtctor, th cost of which is at th momnt quit difficult to stimat, sinc thr will b a hard limit on th siz of th largst undrground cavrn that b xcavatd. Th issus rlatd to bta-bam ar subjct to a dsign study undr Eurisol at th momnt, and thos rlatd to th high powr suprbam (4MW on targt) ar similar to thos of a nutrino factory. From this brif discussion it is vry clar that a cost/physics prformanc/fasibility comparison is ndd; this will b th objct of th upcoming scoping study. 7

8 2 Dscription of th facilitis 2.1 Off axis suprbams: T2K, T2HK and NovA Th facilitis that ar nvisagd immdiatly aftr th CNGS and MINOS-on axis hav bn dsignd so that th nutrino bam nrgy matchs th distanc to th dtctor. Sinc a Wid-band bam on axis has an nrgy which is approximatly 5-10% of th incidnt proton nrgy, with a rapidly dcrasing vnt rat as th horn optics ar dtund to produc a low nrgy spctrum, it is mor advantagous to tun th bam ngy by using th off-axis trick. This is what is bing build for th T2K xprimnt, and nvisagd for th off axis NUMI xprimnt, NOvA. Th T2K (Tokai to Kamioka) xprimnt will aim nutrinos from th Tokai sit to th SuprKamiokaNDE dtctor 295 km away, Figur 6. Th main dsign faturs of th T2K xprimnt li in its bam lin: 1. th nutrino bam is producd by pion dcay from a horn focusd bam, with a systm of thr horns and rflctors. Th dcay tunnl lngth (130 m long) is optimizd for th dcay of 2-8 GV pions and short to minimiz th occurrnc of muon dcays. 2. Th nutrino bam is situatd at an angl of 2-3 dgrs from th dirction of th supr-kamiokand dtctor, assuring a pion dcay pak nrgy of 0.6 GV 3. Th bam lin is quippd with a st of ddicatd on-axis and off-axis dtctors at two diffrnt distancs, 280 mtrs, and possibly, at a latr stag, 2 km as shown in Figur 7. Figur 6: Ovrviw of th J-PARC to SuprKamiokand long baslin xprimnt forsn from Also shown is th K2K bam from KEK to th SuprKamiokand dtctor. 8

9 Th main goals of th xprimnt ar as follows: 1.Th highst priority goal of th xprimnt, is th sarch for th yt unobsrvd nutrino oscillation with th sam frquncy as th atmosphric oscillation (which is known to b mostly du to τ ). This will manifst itslf by apparanc of vnts with an lctron in th final stat. This raction is drivn by th yt unknown mixing angl θ 13, which is also driving th CP violation asymmtry which could b obsrvd in th sam channl by comparing nutrino oscillations to antinutrino oscillations. Th main challng hr is th undrstanding of th backgrounds that produc or mimic an lctromagntic showr: bam from K and muon dcay; π 0 production by nutral currnt vnts. Th main issu is to masur prcisly th bam composition and th rat of backgrounds, so as to b abl to prform a good simulation of th far dtctor. Sinc nuclar ffcts ar rathr important (pion absorption in particular), th matrial should b as nar as possibl to th watr of Supr-Kamiokand. A ddicatd fin grain dtctor is undr construction for th 280m dtctor station, whr th rat is highr. It is xpctd that th snsitivity of th xprimnt will b of th ordr of sin 2 2θ Disapparanc masurmnts, whr th numbr and rat of vnts is studid. This will improv masurmnt of m 2 13 down to a prcision of a or so. Th xact masurmnt of th maximum disapparanc is a prcis masurmnt of sin 2 2θ 23. Ths prcision masurmnts of alrady known quantitis rquir good knowldg of flux shap, absolut nrgy scal, xprimntal nrgy rsolution and of th cross-sction as a function of nrgy. It is absolutly ncssary hr to hav a nar dtctor station with matrial and accptanc as similar as possibl to thos of th far dtctor. Th flux at th 2km station is much mor similar to th SK flux than at 280 m, which constituts, for this particular physics goal, an argumnt in favor of a 2km nar-dtctor, as shown in Figur 7. x E (GV) Figur 7: Schmatic dscription of th dtctors along th T2K bam lin. Th 280m dtctor station is part of th approvd projct. Th 2km station is part of a possibl upgrad. Right: flux shap from th off-axis nutrino bam at 280 m (blu) 2km (rd) of Supr-Kamiokand(black). Th T2K xprimnt is plannd to start in 2009 with a bam intnsity raching 1 MW bam powr on targt aftr a coupl yars. It has an upgrad path which involvs: a 2km nar dtctor station faturing a watr 9

10 Chrnkov dtctor, a muon monitor and a fin grain dtctor (possibly liquid argon); a incras of bam powr up to th maximum fasibl with th acclrator and targt (4 MW bam powr?); and a vry larg watr Chrnkov (HyprKamiokand) with a rich physics programm in proton dcay, atmosphric and suprnova nutrinos and, prhaps, lptonic CP violation, that could b built around in about yars from now. Th difficulty in th xprimnt is that it runs at rlativly low nutrino nrgis, so that th apparanc signal is situatd on top of an intrinsic background from th bam and from π 0 dcays. Th Frmilab NUMI bam is xposd at prsnt to about half a MW of bam powr and an off axis dtctor location has bn idntifid. Th xprimnt would b mad dlibratly complmntary to T2K by using a highr bam nrgy of 1.5 GV. At ths nrgis th channls with on or fw pions in th final stat ar opn and a Watr Chrnkov would suffr too much background. A fully activ liquid scintillator dtctor is bing studid, NovA, with capability to sparat lcrons from chargd and nutral pions. Th highr nrgy wrt to th T2K programm allows to som xtnt and for favorabl valus of th paramtrs, a snsitivity to th mattr ffct. Figur 8 Lft: th 14 mrad off-axis NUMI bam; right: th considrd 20 kton fully activ scintillator NovA dtctor. 10

11 2.2 Th bta-bam + Suprbam facility Figur 9 Bta-bam bas lin dsign, partially using xisting CERN acclrator infrastructur (parts in black). Th bta-bam concpt [Zucchlli] is basd on th acclration, storag and bta-dcay of suitabl ions. Th prfrrd ions ar 6 N ++ 6 Li N 18 F + or 150 Dy Tb Th first on is normal bta dcay and producs a pur wid-band flux of lctron anti-nutrinos. Th scond is th bta-plus dcay and producs a pur lctron nutrino bam. Th third on, lctron captur, is a rlativly nwr ida by Brnabu [Brnabu04, Burgt05] and, for rlativly havy nucli, producs a pur, monochromatic, lctron nutrino bam. Th grat intrst of th bta-bam lis in its purity, and its rlativ practicality [bta-bam]: as long as on contnts onslf with xisting proton machins, th additional rquird infrastructur is limitd to a (quit challnging) high intnsity ion sourc, and a storag ring. Th main drawback is that this lads to rlativly low nrgy nutrinos E = 2 γ E 0 whr E 0 ~ 3 MV is th nrgy of th nutrino in th dcay at rst and γ is th Lorntz boost of th acclratd ion. At th CERN SPS, on can acclrat protons to 450 GV, thus 6 H to 150 GV/u or γ< 150. This limits th nutrino nrgy to about 600 MV, whil alrady rquiring construction of a storag ring with a rigidity quivalnt to that of th SPS. Similarly to th suprbam cas, th dtctor of choic for a low nrgy bta-bam is a larg watr Chrnkov. For highr nrgis th tchnology would chang similarly to a fin graind dtctor, using scintillator or liquid argon. Th highr cross-sction and natural focusing at high nrgy compnsats th mor difficult ralization of massiv sgmntd dtctors. 11

12 Figur 10 Th bta-bam + suprbam + mgaton facility. Top: th schmatic layout; bottom lft: th (non-oscillatd) vnt numbrs for a run of 2 yars of nutrinos and 8 yars of anti-nutrinos; right th snsitivity to sin 2 2θ 13 as a function of th phas δ for this st-up in comparison with T2HK and th nutrino factory. Th high intnsity flux sms rasonably asy to obtain for anti-nutrinos with th 6 H, but 18 N appars to b mor difficult, prhaps smallr by on ordr of magnitud. Th production of Dy sms mor limitd; th application may b a wondrful way to masur cross-sctions and nuclar ffcts dirctly with a monochromatic bam in th nar dtctor. Th suprbam would b a standard horn-focusd nutrino bam from pion dcay, producd from low nrgy protons, with th advantag that th limitd kaon production lads to a small and controllabl compnnt of lctron nutrinos in th bam, from muon dcays. This can actually b varid and monitord by varying th lngth of th dcay tunnl. Thr xist a baslin scnario at CERN for a suprbam + bta bam facility pointing at a mgaton watr Chrnkov in th Frjus laboratory, with a baslin of 130 km. As dscribd by Campagn, th suprbam can b improvd by incrasing th proton bam nrgy to 3.5 GV ovr th original SPL at 2.2 GV (Figur 10 ) It has bn pointd out that bta-bam at highr nris could would b mor powrful, spcially sinc th numbr of vnts pr ton scals as γ 3, as shown in Figur 11. It has bn argud that a bta-bam could 12

13 b run at th Tvatron with a highr nrgy, γ ~350 for th Hlium bam, and 580 for th Non. Clarly th cost of such a facility incrass rapidly with nrgy, sinc a storag ring of quivalnt rigidity would hav to b constructd. This should b takn into account whn imagining high nrgy bta bams. In addition th background issus do incras whn nrgy incrass, sinc pion production (th main background to th muon signal) incrass rapidly with nutrino nrgy. Figur 11 comparativ prformanc of th baslin bta-bam scnario (rd) with a highr nrgy on (γ= 350 for 6 N, as could b acclratd in a 1TV proton acclrator) blu lin. Th sam far dtctor is bing assumd (1 Mton watr Chrnkov) Dtctors Th dtctor for th low nrgy singl flavour bams must b dsignd for th largst possibl mass, whil providing good sparation btwn lctrons, muons and pions. Th watr Chrnkov is an obvious choic, with th cavat alrady mntionnd that it works bst in th nrgy rgion blow th ffctiv pion production thrshold, whr π 0 s mimic lctrons, and π +- mimic muons. (600MV to 1 GV). In this nrgy rang, th watr Chrnkov is unchallngd, Figur 12. At highr nrgis, mor information is ndd and liquid scintillator(nova) and liquid argon dtctors hav bn proposd. A total mass of th ordr of 30 kton sms fasibl for scintillator (Figur 8), and idas for up to 100 kton ar bing considrd for th liquid argon dtctors, Figur 13. Figur 12 Sktch of a Mton watr Chrnkov: hr th Hypr-KamiokaNDE dtctor. Th narly cubic dsign that could b achivd for th Supr-KamiokaNDE dtctor is no longr fasibl du to limitations in undrground xcavations. and on of th dimnsions nds to b xpandd (hr th lngth). 13

14 Figur 13: Schmatic layout of th innr dtctor of a futur Larg Liquid Argon dtctor 2.4 Th nutrino factory In a Nutrino Factory [nufact] muons ar acclratd from an intns sourc to nrgis of svral GV, and injctd in a storag ring with long straight sctions. Th muon dcays: + + and provid a vry wll known flux with nrgis up to th muon nrgy itslf. Th ovrall layout is shown in Figur 14. Figur 14 Lft: Schmatic layout of a Nutrino Factory; right: possibl long baslin scnarios for a Europan basd facility. Nutrino Factory dsigns hav bn proposd in Europ [Aut99], [Gru02], th US [MuColl] [StudyI][StudyII], and Japan [Japnufact]. Of th thr dsigns, th on in th US is th most dvlopd, and w will us it as a xampl in gnral with a fw xcptions. Th conclusions of ths studis is that, providd sufficint rsourcs, an acclrator complx capabl of producing and storing mor than muons pr yar can b built. Th Nutrino Factory consists of th following subsystms: 14

15 Proton Drivr. Provids 1-4 MW of protons on a pion production targt. For th Nutrino Factory application th nrgy of th bam is not critical, sinc it has bn shown that th production of pions is roughly proportional to bam powr. Th tim structur of th proton bam has to b matchd with th tim sprad inducd by pion dcay (1-2 ns); for a linac drivr such as th SPL, this rquirs an additional accumulator and comprssor ring. Targt, Captur and Dcay. A high-powr targt sits within a 20T suprconducting solnoid, which capturs th pions. Th high magntic fild smoothly dcrass to 1.75T downstram of th targt, matching into a long solnoid dcay channl. A dsign with horn collction has bn proposd at CERN for th Nutrino Factory, with th bnfit that it can b also usd for a suprbam dsign. Th advantag of th horn that it sign-slcts th pions and muons is compnsatd by th fact that in a Nutrino Factory dsign on could acclrat both signs of muons, thus doubling th availabl flux. Bunching and Phas Rotation. Th muons from th dcaying pions ar bunchd using a systm of rf cavitis with frquncis that vary along th channl. A scond sris of rf cavitis with highr gradints is usd to rotat th bam in longitudinal phas-spac, rducing th nrgy sprad of th muons. Cooling. A solnoid focusing channl with high-gradint 201 MHz rf cavitis and ithr liquid-hydrogn or LiH absorbrs is usd to rduc th transvrs phas-spac occupid by th bam. Th muons los, by de/dx losss, both longitudinal- and transvrs-momntum as thy pass through th absorbrs. Th longitudinal momntum is rplacd by r-acclration in th rf cavitis. Acclration. Th cntral momntum of th muons xiting th cooling channl is 220 MV/c. A suprconducting linac with solnoid focusing is usd to rais th nrgy to 1.5 GV. Thraftr, a Rcirculating Linar Acclrator raiss th nrgy to 5 GV, and a pair of Fixd-Fild Altrnating Gradint rings acclrat th bam to at last 20 GV. Storag Ring. A compact ractrack gomtry ring is usd, in which 35% of th muons dcay in th nutrino bamforming straight sction. If both signs ar acclratd, on can injct in two suprimposd rings or in two paralll straight sctions. This schm producs ovr usful muon dcays pr oprational yar and pr straight in a triangular gomtry. Th Europan Nutrino Factory dsign is similar to th US dsign, but diffrs in th tchnologis chosn to implmnt th subsystms. Th Japans dsign is vry diffrnt, and uss vry larg accptanc acclrators rathr than cooling. An important Nutrino Factory R&D ffort is ongoing in Europ, Japan, and th U.S. sinc a fw yars. Significant progrss has bn mad towards optimizing th dsign, dvloping and tsting th rquird componnts, and rducing th cost. To illustrat this progrss, th cost stimat for a rcnt updat of th US dsign [APS04] is compard in Tabl 2 with th corrsponding cost for th prvious Study II US dsign [Study II]. It should b notd that th Study II dsign cost was basd on a significant amount of nginring input to nsur dsign fasibility and stablish a good cost basis. Nutrino Factory R&D has rachd a critical stag in which support is rquird for two ky intrnational xprimnts (MICE [MICE] and Targtry [targt-xp]) and a third-gnration intrnational dsign study. If this support is forthcoming, a Nutrino Factory could b addd to th Nutrino Physics roadmap in lss than a dcad. Tabl 2 Comparison of unloadd Nutrino Factory costs stimats in M$ for th US Study II dsign and improvmnt stimatd for th latst updatd US dsign. Costs ar shown including A: th whol complx; B no Proton Drivr andc: noproton drivr and no Targt station in th stimats. Tabl from Rf. [APS04]. Costs in M$ A B C Old stimat from Study II Multiplicativ factor for nw stimat

16 Oscillations physics Considring a Nutrino Factory with simultanous bams of positiv and ngativ muons, th following 12 oscillation procsss can b studid. + + disapparanc apparanc: platinum channl? τ τ τ τ apparanc (atmosphric oscillation) disapparranc apparanc: goldn channl apparanc: silvr channl An important fatur of th Nutrino Factory is th possibility of having opposit muon chargs circulating in th ring, thrfor allowing also th study of th chargd-conjugatd procsss of thos abov. Of cours th nutrinos coming from dcays of muons of diffrnt charg must no b confusd with ach othr, this can b don by timing providd th storag ring is adquatly dsignd. Figur 15 Nutrino factory with both signs acclratd and stord. Lft: in th rac-track gomtry, th two long straight sctions must point toward th sam far dtctor, but two nar dtctor stations ar rquird. It may b mor practical to produc both dcays in th sam straight sction, onto th sam nar dtctor, as in a doubl ring or in a dog-bon gomtry (middl). For th triangl, on must fors two suprposd rings or spcial magnts for th bnds. [Blondl03] It rmains to sparat th two nutrno flavours that ar always simultanously prsnt. Idntification of th flavour of th lpton producd in chargd-currnt intractions is not sufficint and on nds to masur its charg. For muons in th final stat (coming from intractions of from dcays of τ ), this can b don radily using a magntic dtctor of dsign similar to that of th CDHS or MINOS xprimnts, for which by that tim on can safly assum that it could b built with a mass of th ordr of 50 ktons. Many studis hav bn prformd undr this hypothsis, whr th main discovry channl is th wrong sign muon also calld goldn channl [Crvra00]. Compard with convntional nutrino bams, Nutrino factoris yild highr signal rats with lowr background fractions and lowr systmatic uncrtaintis. Ths charactristics nabl Nutrino Factory xprimnts to b snsitiv to valus of θ 13 that ar byond th rach of any othr. Studis (s.g. [Hubr03]) hav shown that a non-zro valu of sin2 θ 13 could b masurd for valus as small as O(10-4 ). In addition, both th nutrino mass hirarchy and CP violation in th lpton sctor could b masurd ovr this ntir rang. Evn if θ 13 = 0 th probability for oscillations in a long-baslin xprimnt is finit, and a Nutrino Factory would still mak th first obsrvation of it in an apparanc xprimnt, and put a sufficintly stringnt limit on th magnitud of θ 13 to suggst prhaps th prsnc of a nw consrvation law. For th masurmnt of th quantitis θ 13 and δ, it has bn shown that th goldn obsrvabls ar th oscillation probabilitis and at baslins, L, and nrgis, E, in th 16

17 atmosphric rang E/L m Th sign( m 2 23) can b dtrmind with ths sam transitions givn th high nrgy and long baslins availabl. (Figur 16) Figur 16 Th snsitivity rachs as functions of sin 2 2 θ 13 for sin 2 2 θ 13 itslf, th nutrino mass hirarchy, and maximal CP violation for ach of th indicatd baslin combinations. Th bars show th rangs in sin 2 2 θ 13 whr snsitivity to th corrsponding quantity can b achivd at th 3σ CL. Th dark (rd) bars show th variation in th rsult as m 2 21 is varid within its prsnt uncrtainty. Figur from [Hubr03]. Th abov studis wr mad only unsing th goldn channl, and for vry high muon momntum (cut at 4-5 GV). A mor granular dtctor may b abl to ithr dtct lctrons, prhaps vn masur thir charg ( platinum channl) or dtct tau lptons and masur thir charg ( silvr channl). In th studis mad assuming a larg liguid argon dtctor ([Buno00], th dtctd vnts could b classifid in four classs: Chargd-currnt lctrons, Right-sign muons, Wrong-sign muons, Evnts with no lptons. An xampl of th st of nrgy spctra for ths classs, for positiv and ngativ muons circulating in th ring, is givn in Figur 17. Figur 17 : Four classs of vnts studid in a liquid argon TPC with muon charg idntification. From th top, lft to right: vnts with high-nrgy lctrons, right-sign muons, wrong-sign muons, no chargd lptons [Buno00]. Th baslin hr is 7200 km. 17

18 Prforming masurmnts at potntial nutrino factoris will fac th xistnc of corrlations and dgnracis in paramtr spac[crvra00],[burgut01],[minakata01], [Bargr02] which mak th simultanous dtrmination of all th unknowns rathr difficult. Th importanc of having good nutrino nrgy rsolution or combining th masurmnts of th goldn oscillation probabilitis at svral xprimnts with diffrnt < E /L > (or diffrnt mattr ffcts) hav bn proposd to ovrcom this problm [Burgut01],[Bargr02],[Burgut02]. In addition, th masurmnt of th silvr channls [Donini02] bsids th goldn on, τ, τ although it is xprimntally mor challnging, is xtrmly powrful in rducing ths corrlations. Th silvr channl also provids a tst of unitarity of th Nutrino mixing matrix! In fact, it has bn shown that whil th combination of bta-bam and SuprBam could not hlp in solving th dgnracis, th combination of on of thm with th Nutrino Factory Goldn and Silvr channl can, instad, b usd to solv compltly th ightfold dgnracy. It is vn advocatd, although full dmonstration is ndd, that with a Nutirno Factory with two baslins and dtctors abl to masur both th goldn and silvr channls in addition to th disapparanc channls, a fully unabiuous dtrmination of oscillation paramtrs could b achivd. Figur 18 Solving dgnracis (from [Rigolin04]). Th paramtr spac shown is th variation { θ 13, δ CP } around th tru solution in th {θ 13, δ CP } plan. Th lins show th locus whr th sam numbr of vnts would b obsrvd. Full lins, nutrino xposur; dashd lins antinutrino xposur. On th lft, th rd and blu lins show two diffrnt bas lins (730 and 3500 km) whil on th right th rd and blu lins show th goldn and silvr channl. Ths studis wr don for th Nutrino Factory som yars ago for a muon nrgy of E =20-50 GV and a baslin for th goldn masurmnt of a fw thousand kilomtrs[crvra00]. Th combination of this masurmnt, using a 40 KTon iron calorimtr [Crvra00a], plus th silvr on in an Opra-lik tau-nutrino dtctor [Donini02] rsults in a grat physics potntial. Th snsitivity to sin 2 θ 13 is blow 10-4 and thr is a 99% CL discovry potntial for CP violation if δ> In addition, th atmosphric paramtrs can b dtrmind with a 1% prcision and th sign of m 2 23 can b masurd in a larg rang of paramtr spac. Ths studis will nd to b actualizd to tak into account progrss both in acclrator and dtctor dsign. High-prcision nutrino scattring As discussd in [Mangano01], [Bigi01], th nutrino bams at th nd of th straight sction of a Nutrino Factory offr an improvmnt in flux by svral ordrs of magnitud ovr convntional bams, allowing svral tims 10 8 vnts to b collctd pr kilogram and pr yar (Figur 19). This could allow a nw gnration of nutrino xprimnts, whith dtaild studis of nuclon structur, nuclar ffcts, spin structur functions and final stat xclusiv procsss. Prcision tsts of th Standard Modl could b carrid out in nutrino scattring on nuclon or lctron targt, as wll as a prcis dtrmination of nutrino cross-sctions and flux monitoring with prmil accuracy. 18

19 Figur 19 Evnt rats at th xit of th straight sctions in a Nutrino Factory. Not th scal. Muon physics A high-intnsity proton sourc could crtainly produc many low-nrgy muons [Aysto01] and thus, providd th bam and xprimnts can b dsignd to do so, provid opportunitis to xplor rar dcays, such as γ,, or th muon convrsion N N, which ar lpton-numbr-violating procsss. Whil th S- Saw mchanism provids a vry appaling xplanation of nutrino masss and mixings, its inclusion in suprsymmtric modls almost invariably lads to prdictions in xcss or clos to th prsnt limits for ths procsss. It is thrfor quit possibl that on of ths procsss will b discovrd in th upcoming gnration of xprimnts (MEG [MEG] at PSI, MECO at BNL) in which cas a dtaild study would bcom mandatory. If not, furthr sarch with highr snsitivity would b in dmand. It should b mphasizd that th thr procsss ar actually snsitiv to diffrnt paramtrs of ths modls, and thus complmntary from both th xprimntal and thortical points of viw. Anothr fundamntal sarch would clarly b th sarch for a muon lctric dipol momnt (EDM), which would rquir modulation of a transvrs lctric fild for muons situatd alrady at th magic vlocity whr th magntic prcssion and th anomalous (g-2) prcssion mutually cancl. Muon Collidrs Finally, it is worth kping in mind that th Nutrino Factory is th first stp towards muon collidrs. As shown in [muoncollidr], th rlvant charactristics of muons ar that, compard to lctrons, i) thy hav a much bttr dfind nrgy, sinc thy hardly undrgo synchrotron radiation or bamstrahlung, ii) thir coupling to th Higgs bosons is multiplid by th ratio (m/m)2, thus allowing s-channl production with a usful rat. Ths rmarkabl proprtis mak muon collidrs suprb tools for th study of Higgs rsonancs, spcially if, as prdictd in suprsymmtry, thr xist a pair H, A of opposit CP quantum numbrs which ar narly dgnrat in mass. Th study of this systm is xtrmly difficult with any othr machin and a uniqu invstigation of th possibl CP violation in th Higgs systm would bcom possibl. 19

20 3 Comparison of facilitis and opn qustions Th prformanc of various suprbams, btabams and Nutrino Factoris hav bn compard xtnsivly with varying mthods and prsntations. On st of comparativ plots wr prpard for th MMW workshop, and ar shown in Figur 20. Anothr st of plots could b sn at NUFACT05, and ar shown in Figur 21. Th comparison of ths curvs points to a numbr of qustions and commnts. Figur 20 rlativ snsitivity to θ 13 (top) and to th CP violating phas δ (bottom), of various options for futur nutrino facilitis basd on a high intnsity proton drivr from th 2004 MMW workshop. Figur 21 comparison of diffrnt options for futur nutrino facilitis. On th lft, th snsitivity to sin 2 2θ 13 dscibd with th convntion of th MTU group [Lindnr], whr: th intrinsic statistical snsitivity of th xprimnt can b radout on th lft of th band corrponding to ach considrd xprimnt (this assums that all othr oscillation paramtrs ar infinitly and unambiguously wll known); th xprimntal systmatics ar shown nxt (including thos from mattr ffcts) as a blu band; th ffct of othr paramtr uncrtaintis is shown by th grn bad, th ffct of ambiguitis in cas of multipl solutions in paramtr spac ar shown as a yllow band. On th right, prcision in th masurmnt of th CP phas δ, xprssd as th siz of th 90% CL spot in paramtr spac (for small covrag this would b about thr tims th rror). 20

21 It is clar that from th first st of plots (Figur 20) on would conclud that a nutrino factory is th most powrful dvic to masur CP violation, dtrmin th mass hirarchy and xtract th bst prcision on sin 2 2θ 13, rgardlss of th valu of this mixing angl. If this is corrct, thn on would conclud that thr is no nd to wait for th nxt gnration of xprimnts to go forward with it. Th scond st of plots sm to indicat on th contrary that th supriority of th nutrino factory is a sin 2 2θ 13 dpndnt statmnt and that it is urgnt to wait. At this point on could argu that th braking point is around sin 2 2θ 13 ~ 0.01 and that th combination of MINOS@NUMI, CNGS, th nxt ractor xprimnt and th first runs of T2K should giv alrady a clar indication of whr this paramtr lis by 2010 or so, Figur 5, and that on should gt prpard in any cas. Nvrthlss, a closr invstigation of ths conclusions is ncssary and instructiv. As Mzztto pointd out in his NUFACT05 prsntation, and for th rason advocatd arlir (Figur 4), masuring th CP violation for larg valus of θ 13 is not too difficult from th point of viw of statistics, but is xtrmly challnging from th point of viw of systmatic rrors, bcaus th asymmtry is small. As pointd out arlir, on solution is to go for th scond maximum, whr th ffct is largr but th statistics much smallr. In addition, th intrplay btwn mattr ffcts and CP violation rquirs ithr a good knowldg of mattr ffcts from xtrnal information, or a mor sophisticatd analysis to xtract thm from th oscillation data thmslvs as waas don in [Campanlli00]. Th nxt gnration of studis should clarly addrss th issus of systmatic rrors in a systmatic and, as always whn daling with systmatics, crativ way. Th discussion ncssary to stablish rasonabl systmatic rrors masuring th CP or T asymmtry should includ th following qustions: 1. how dos on masur th cross-sction*fficincy of th apparanc channl in a bam with only on flavor? (suprbam or bta-bam alon) 2. What kind of nar dtctor will b ndd? (it sms impossibl to talk about flux systmatics without a strawman dsign for th nar dtctor) What is th nrgy snsitivity of ths issus which should b quit srious at low nrgis (E ~ fw MV )and gradually bcom asir at high Enrgis. Th nutrino factory provids all channls in th sam bam lin/dtctor, but can on mak us of this? In ordr to go furthr, on must addrss a st of spcific rmarks and qustions to th various typs of facilitis 3.1 Nutrino factory issus. On must rmmbr that most of th nutrino factory studis hav bn mad in th yars , and would highly bnfit from a rfrshd look. Thr is no ordring in th following qustions, and thr should probably b som rflction on undrstanding which on should b tackld first. 1.Sinc th arly part of th studis it has bn advocatd that having two diffrnt locations allows to dcifr th mattr ffct from th CP violation, as thy hav diffrnt distanc dpndnc. With th ralization that th nrgy distribution could also rsolv this issu, do w rally nd far locations at two diffrnt distancs? 2. Th dtctor that was simulatd (a larg magntizd iron calorimtr) and th analysis that was prformd in th studis so far hav advocatd a muon momntum cut at about 4-5 GV, in ordr to gt a vry clan and background fr sampl of wrong-sign muons. This is clarly favorabl to obtaining a vry 21

22 good snsitivity to θ 13, but lads to a poor fficincy at low momntum. Prhaps as a consqunc, th optimal distanc was found to b about 3000km, for which th first oscillation maximum is locatd at about 6GV. Th scond oscillation maximum at 2 GV is thn compltly lost. Can this b improvd, by a mor finly sgmntd iron calorimtr, or a magntizd fin-graind dtctor (fully activ scintillator or Liquid argon dtctor inbddd in a magntic fild)? 3. Can on rally liminat all dgnracis by combination of nrgy distribution and analysis of diffrnt channls (tau, muon, lctron, both signs, NC ) and what is th nd of two baslin to do so? 4.what ar th systmatics on flux control? (Th CERN yllow rport claims that a prcision of 10-3 should b achivabl) 5. what ar th a priori systmatics on th knowldg of th mattr ffct? How can this b dtrmind from th data, and what ar th conditions on th xprimnt to b abl to do so? 6. What is th bst baslin and consquntly optimal stord muon nrgy? This is an important qustion as this is a cost-drivr in th acclrator (in study II th cost of nutrino factory was givn as ~ 1500M$ + 400M$*E/20GV) 3.2 Suprbam+bta-bam issus 1.Th first qustion of cours is that of finding th nrgy and distanc combination that allows both btabam and suprbam to b usd optimally. Th difficulty with a low nrgy scnario such as CERN-Fréjus is that th short baslin imposs an oscillation maximum at E ~250 MV. This is barly abov th muon Chrnkov Thrshold, and commnsurat with both th Frmi momntum and th muon mass, thus making it vry snsitiv to nuclar ffcts, muon mass corrction tc Bfor bing considrd sriously, this xprimnt must b validatd by a convincing study of systmatic rrors and of th mans to control thm. A stratgy of ancillary masurmnts in th nar dtctor station could b th answr to this issu. 2. On of th argumnts in favour of th bta-bam is that th production targts ncssary for ion production ar fficint nough not to rquir vry high primary proton powr. This advantag is rducd if a 4MW suprbam is ncssary to mastr systmatic rrors. Th qustion is thn: what is th importanc of th suprbam in this schm? Is is only th bauty of T violation or much incrasd snsitivity or th nd to hav a (known) sourc of muon nutrinos to calibrat th cross-sctions and fficincis of th dtctor to th goldn signal? 3. At which nutrino nrgy can on bgin to us th vnt nrgy distribution, which is a vry powrful cross-chck of th xprimnt? Hr again, th ffct of Frmi motion appars, in that it affcts th ability to rconstruct th vnt kinmatics. Hr again, what is th impact of muon Chrnkov thrshold? 4. Should nrgy rmain an adjustabl paramtr onc th long baslin distanc has bn chosn? On could imagin that this could b achivd by movabl horns for th WBB, by varying th bam axis for th off-axis bam, or by changing th nrgy of th storag ring in th bta bam. 5. What is th rlationship btwn bta-bam and suprbam nrgis, vs intnsity? 6. What is rally th cost of th dtctor? For th watr Chrnkov, what PM covrag is ndd as function of nutrino nrgy? For th Liquid Argon or scintillator altrnativs, can thy, thanks to bttr granularity and accptanc, compt with th watr Chrnkov givn th unavoidabl limitations in dtctor mass? 22

23 6. Conclusions Nutrinos hav unvild for us a nw layr of rality byond th Standard Modl. It is possibl that th answr to thir xtraordinary small masss is trivial, it may hav its origin at a much highr scal that what will b invstigatd with th nxt gnrations of acclrators (LHC, ILC, CLIC). It mayb that CP/T violation will b obsrvd and it may b that nutrinos hav a diffrnt concpt of hirarchy than chargd frmions. Ths qustions ar simpl but fundamntal. Thy justify a considrabl invstmnt in tim and rsourcs from th community. Thr xist an opportunity for a powrful facility to b dcidd togthr and built in th nxt dcad, and th qustion is: which on? Th scoping study will not answr this qustion but should idntify th work that will b ndd to mak this dcision in th bst possibl way. I hop this short rflction and list of qustions will prov usful. Acknowldgmnts This prsntation and articl summariz th work of svral hundrd of mmbrs of th CERN and ECFA studis of a Nutrino Factory Complx, which was summarizd in th vry complt [ECFArport], non of which would hav bn possibl without th pionring work of th Nutrino Factory and Muon Collidr collaboration [MuColl]. W also acknowldg th support of th Europan Community-Rsarch Infrastructur Activity undr th FP6 Structuring th Europan Rsarch Ara programm (CARE, contract numbr RII3-CT ) 23

24 Rfrncs [Apollonio02] [APS04] M. Apollonio t al., Oscillation Physics with a Nutrino Factory arxiv:hp-ph/ in ECFA/CERN Studis of a Europan Nutrino Factory Complx Blondl, A (d.) t al.cern ECFA , p85 Nutrino Factory and Bta Bam Exprimnts and Dvlopmnts, (Eds. S. Gr and M. Zisman), Rport of th Nutrino Factory and Bta Bam Working Group, APS Multi-Divisional Study of th Physics of Nutrinos, July [Aut99] B. Autin, A. Blondl and J. Ellis ds, CERN yllow rport CERN 99-02, ECFA [Aysto01] J. Aysto t al., Physics with Low-Enrgy Muons at a Nutrino Factory Complx, CERN-TH/ , in ECFA/CERN Studis of a Europan Nutrino Factory Complx Blondl, A (d.) t al.cern ECFA , p259. [Barbiri94] R. Barbiri and L.J. Hall Phys. Ltt. B338 (1994) 212 [Bargr02] V. Bargr, S. Gr, R. Raja, K. Whisnant, Phys. Rv. D63 (2001) [Bargr02a] [BENE] [Bigi01] [Burgt02] [Burgut01] [Burgut02] [Burgut03] V. Bargr, D. Marfatia and K. Whisnant, ``Braking ight-fold dgnracis in nutrino CP violation, mixing, and mass hirarchy,'' Phys. Rv. D65 (2002) , [arxiv:hp-ph/ ]. Bams for Europan Nutrino Exprimnts is a Nworking Activity ( supportd by th EC and most major Europan Agncis in th framwork of th FP6 Intgratd Activity CARE (Coordinatd Acclrator R&D in Europ) Th scop of BENE is also dscribd in mor dtail in th following documnt: I. I. Y. Bigi t al., Th Potntial for Nutrino Physics at Muon Collidrs and Ddicatd High Currnt Muon Storag Rings Phys. Rpt. 371 (2002) 151 [arxiv:hp-ph/ ]. J. Burgut-Castll t al., hp-ph/ J. Burgut-Castll t al, Nucl. Phys. B608 (2001) 301 [arxiv:hp-ph/ ]. J. Burgut-Castll t al, Nucl. Phys. B646 (2002) 301, [arxiv:hp-ph/ ]. J. Burgut-Castll, D. Caspr, J.J. Gómz-Cadnas, P. Hrnándz, F. Sanchz, hp-ph/ , to appar in Nucl. Phys. B. [CARE] FP6 Intgratd Activity (Coordinatd Acclrator R&D in Europ) [Crvra] Invitd Talk at Nufact04, th Int. Workshop on Nutrino Factoris and Suprbrams, Osaka, July 2004, [Crvra00] A. Crvra t al, Nucl. Phys. B579 (2000) 17. [Crvra00a] A. Crvra, F. Dydak and J.J. Gomz-Cadnas, Nucl. Instr. Mth. A 451 (2000) 123. [Donini02] A. Donini, D. Mloni and P. Migliozzi, hp-ph/ [Donini02] A. Donini, D. Mloni, P. Migliozzi, Nucl. Phys. B646 (2002) 321, [arxiv:hp-ph/ ]; D. Autiro t al., ``Th synrgy of th goldn and silvr channls at th Nutrino Factory,'' arxiv:hpph/ [ECFArport] ECFA/CERN studis of a Europan Nutrino Factory complx, A. Blondl t al, d CERN (2004) [Gr98] S. Gr, PRD 57, 6989 (1998) [Gilardoni] S. Gilardoni, PhD thsis Univrsity of Gnva (2004). S also Nutrino Factory nots 4, 38, 42, 77, 80, 81, 86, 126, 129, 134,138 accssibl from [Gru02] [Hubr02] P. Grubr t al, Th Study of a Europan Nutrino Factory Complx, Nutrino Factory Not 103(2002) CERN/PS/ (PP), in ECFA/CERN Studis of a Europan Nutrino Factory Complx Blondl, A (d.) t al.cern ECFA , p7 P. Hubr, M. Lindnr and W. Wintr, Nucl. Phys. B645 (2002) 3, [arxiv:hp-ph/ ]. 24

25 [Hubr03] [Japnufact] P. Hubr and W. Wintr; Phys. Rv. D68, (2003); hp/ph A Fasibility Study of A Nutrino Factory in Japan, Y. Kuno, d., [KamLAND02] K. Eguchi t al., KamLAND Coll., First Rsults from KamLAND: Evidnc for Ractor Anti- Nutrino Disapparanc, Phys. Rv. Ltt. 90 (2003) hp-x/ [KamLAND04] KamLAND collaboration, Masurmnt of nutrino oscillations with KamLAND: Evidnc of spctral distortion, hp-x/ [lptognsis] M. Fukugita and T. Yanagida, Phys. Ltt. 174B (1986) 45. [Lindnr02] M. Lindnr, Th physics potntial of futur long baslin nutrino oscillation xprimnts, to appar in Nutrino Mass, Springr Tracts in Modrn Physics, d. G. Altarlli and K. Wintr, hpph/ (2002) [Lombardi] [Mangano01] [MEG] A. Lombardi, A MHz Systm for Phas Rotation and Cooling, Nufact Not 34. S also nots 41, 102, M. L. Mangano t al., Physics at th front-nd of a Nutrino Factory: a quantitativ appraisal arxiv:hp-ph/ , in ECFA/CERN Studis of a Europan Nutrino Factory Complx Blondl, A (d.) t al.cern ECFA , p187 Th MEG xprimnt: sarch for th m g at PSI, Sptmbr 2002, availabl at [Mzztto03] M. Mzztto, J. Phys. G.29 (2003) 1771 and [MICE] [MMW] Th Intrnational Muon Ionization Exprimnt MICE, Workshop on Physics at a Multi Mgawatt Proton drivr, CERN-SPSC-2004-SPSC-M-722, [MuColl] Th Muon Collidr and Nutrino Factory Collaboration, s th wb sit which contains also rfrncs to svral physics studis. [Mucool] [muoncollidr] [Muons_wb] [nufact] Th Muon Cooling Exprimntal R&D S for instanc S. Kramlt al,,physics opportunitis at m+m- Higgs factoris, in [ECFArport], p S. Gr, Phys. Rv. D57 (1998) 6989; A. D Rújula, M.B. Gavla and P. Hrnándz, Nucl. Phys. B547 (1999) 21; A. Blondl t al., Nucl. Instrum. Mthods Phys. Rs., A 451 (2000) 102; For rcnt rviws s M. Apollonio, t al, in CERN-04/02, (2004) arxiv:hp-x/ ; J. J. Gómz- Cadnas and D.A. Harris, ``Physics opportunitis at nutrino factoris,'' Ann. Rv. Nucl. Part. Sci. 52} (2002) 253 and th annual procdings of th Intrnational Nufact Workshop. [NuFactPhys] B. Autin, A. Blondl and J. Ellis ds, CERN yllow rport CERN 99-02, ECFA ; C. M. Anknbrandt t al., Phys. Rv. ST Accl. Bams 2, (1999); A. Blondl t al., Nucl. Instrum. Mthods Phys. Rs., A 451 (2000) 102; C. Albright t al., FERMILAB-FN-692, hp-x/ ; D. Harris t al., Snowmass 2001 Summary, hp-ph/ ; A. Crvra t al., Nucl. Phys. B579, 17 (2000), Erratum-ibid.B593: ,2001; M. Koik and J. Sato, Phys. Rv. D62 (2000) [Rigolin04] [Ruj99] S. Rigolin, Why car about (θ13, δ) dgnracy at futur nutrino xprimnts, Rncontrs d Moriond 2004, to appar in th procdings (2004), arxiv:hp-ph/ A. D Rujula, M.B. Gavla, P. Hrnandz, Nucl. Phys. B547 (1999) 21, arxiv: hp-ph/ [SNO01] Q. R. Ahmad t al., SNO Coll, Phys. Rv. Ltt. 87, (2001) [SNO02] [StudyI] Q. R. Ahmad t al., SNO Coll., nucl-x/ Fasibility Study on a Nutrino Sourc Basd on a Muon Storag Ring, D.Finly, N.Holtkamp, ds. (2000), [StudyII] Fasibility Study-II of a Muon-Basd Nutrino Sourc, S. Ozaki, R. Palmr, M. Zisman, and J. Gallardo, ds. BNL-52623, Jun 2001, availabl at rport.html ; M.M. Alsharo a t al., Phys. Rv. ST Accl. Bmas 6, (2003). [targt-xp] R.J. Bnntt t al, Studis of a targt systm for a 4MW 24 GV proton bam, CERN-INTC proposal , April