Neutrino Oscillation Experiments at Reactors and Accelerators

Transcription

1 Nutrino Oscillation Exprimnts at Ractors and Acclrators Gaston Wilqut IIHE-Univrsité Libr d Bruxlls IV èms Rncontrs du Vitnam, Hanoi, July 2000

2 Contnts CHOOZ and PALO VERDE long baslin xprimnts Sarch for disapparanc at ractors. Larg mixing angl, small m 2 (>10-3 V 2 ) KARMEN2 and LSND short baslin xprimnts Sarch for µ oscillation in low nrgy nutrino bams. High snsitivity, small mixing angl, larg m 2 (fw V 2 ) CHORUS and NOMAD short baslin xprimnts Sarch for µ τ oscillation in high nrgy nutrino bams. High snsitivity, small mixing angl, larg m 2 (fw tns V 2 )

3 To-morrow Byron Lundbrg will giv a sminar at FrmiLab on "Rsults from DONUT: First Dirct Evidnc of th Tau Nutrino This was xpctd and did no happn xplicitly in Sudbury at Nutrino 2000

4 Nutrino Oscillation Exprimnts at Nuclar Ractors Long bas lin xprimnts at nuclar powr plants of Chooz and Palo Vrd Motivation: disapparanc in ( m 2, sin 2 2 θ) paramtr spac indicatd by µ disapparanc in atmosphric xprimnts µ?

5 Nutrino Oscillation at Ractors: pros and cons E fw MV Accss to low m 2 at mdium L Blow µ, τ thrsholds: only disapparanc High flux, but small σ 4π sourc dtctor mass L 2 P = 1GW lc 3.3GW 3.3GW Fission rat 200MV E 3 MV m V L 1000 m 2 2 thrm s x s 1 Disapparanc good knowldg of absolut flux and + nrgy spctrum or multi-l xprimnt ( 2 dtctors or ractors) no snsitivity at high m 2 (not srious problm with m V 2 Chp and wll known sourc Calculatd and masurd flux and nrgy spctrum at L=0 known to ~ 2% (Bugy 1995) Intraction spctrum cm 2 E < thrsh E + = 1.8 > 3 MV MV

6 Dtction of nutrinos from nuclar ractors 1953 : F.Rins and C.L. Cowans discovr th nutrino at Savannah Rivr nuclar powr plant Dtctors -vssl filld with liquid scintillator dopd with nutronphag -shilding (bunkr, undrground) + activ vto: cosmic rays, ractor n, natural radioactivity E < thrsh E + Signal = 1.8 MV > 3 MV nuclar captur + p γ 's ( + n E γ known) Spac and dlayd tim corrlation sc in tilla tio n γ ' s + - annihilation : 2 γ of kv Crnkov light

7 Th Long Bas Lin CHOOZ Exprimnt Phys. Lt. B466 (1999) 415

8 CHOOZ dtctor -1 dtctor - 2 ractors (8.5GW) : L= 998, 1114m L=116.7m -rock ovrburdn: 300 m watr quivalnt 0.4 cosmic µ m -2 s -1-5 tons Gd-dopd liquid scintillatior (0.09%) -17 tons liquid scintillator : contain γ from n PMT radioactivity shild -90 tons activ cosmic-ray muon vto E γ = 8MV 90t 5t 17t

9 Evnt rats: full powr: 24.7±0.7 vnts/day ractors off: 1.2 vnts/day Data taking: April July 1998 Ractor 1 ON h 8295 GWh Ractor 2 ON Ractors 1 & 2 ON Ractors OFF Background stimats Rspons calibration: γ, n and γ-n radioactiv sourcs ( 60 Co, 252 Cf, Am/B) E abs n tim dpndnc monitoring ( E 8MV) with n from cosmic : σ E = 0.5 MV γ =

10 Ractor ON Ractor OFF No vnt slction n-lik E (MV) rgion n-lik E (MV) rgion Main background fast spallation n in rock + p from n scattring ( + lik) + n captur + -lik E (MV) + -lik E (MV) n-lik E (MV) rgion n-lik E (MV) rgion > 30 cm from wall, n - + distanc < 100 cm n - + dlay in (2-100) µs E( + -lik) in (1.3-8) MV E(n-lik) in (6-12) MV 2991 candidats (287 ractors off) Efficincy: 69.8%

11 flux known to 1.4% E + spctrum daily volution of cor isotopic volution instantanous fission rat from thrmal powr yild from masurd β spctra of main isotops + invrs β-dcay cross-sction simulation of dtctor rspons ractor ON data MC R OFF background subtractd E spctrum masurd = + R E + spctrum xpctd E + (MV) E + (MV) E + (MV) R = ± (stat) ± (syst) No oscillation signal

12 Analysis Mthods A - Compar unfoldd E + absolut spctra of both ractors to xpctation Systmatic uncrtainty on absolut normalisation: ~2% Two indpndnt masurmnts B - Ratio of spctra Most systmatic cancl No snsitivity at larg m 2 C - Compar unfoldd E + spctra shaps of both ractors to xpctation Intrmdiat snsitivity

13 δm 2 (V 2 ) x m ( V 2 2 ) 10-1 Chooz xclusion plot A absolut spctra B spctra ratio 10-2 C spctra shap Kamiokand 90% 10-3 analysis A analysis B analysis C 90% CL Kamiokand (multi-gv) % CL Kamiokand (sub+multi-gv) sin 2 (2θ) sin 2 2θ

14 Th Long Bas Lin Palo Vrd Exprimnt G.Gratta Nutrino 2000 F.Bohm t al. hp-x/000322

15 -1 dtctor - 3 ractors (11.6 GW) : L= 750, 890m L= 110m Palo Vrd dtctor -rock ovrburdn: 32 m watr quivalnt 22 cosmic µ m -2 s tons Gd-dopd liquid scintillation (0.1%) E γ = 8MV - oil and 105 tons watr buffr: γ and n shild shild PM radioactivity -optically sgmntd dtctor (900x12.7x25.4 cm 3 ) background supprssion

16 Difficulty : No priod with all ractors off to masur simply th ractors off background. Analysis basd on th knowldg of th flux form th known ractors powr Tru xpctd vnt numbr compard to Obsrvd numbr of candidats corrctd for dtctor fficincis (MC) Unknowns : -Background -Ovrall normalisation within systmatic uncrtainty fficincy R = (stat) (sys) No oscillation

17 Run till nd Summr nw rducd powr priods Not likly to do bttr than Chooz

18 Thr nutrinos familis analysis Ractor xprimnts xclud two-family µ oscillation in paramtrs rgion whr µ dficit in atmosphric xprimnts favours two-family µ τ (or s ) (at last) 3-flavour analysis

19 3-flavour mixing paramtrization 3 = α Uαkk k = 1, m 3 kk' 2 U 6(8)paramtrs µ = 2 Uαk = 1 α =, µ, τ 3 Uαk k = 1, Dirac (Majorana) τ 3 1(3)phass = m ' = 0 kk ' k,k k CKM-lik matrix standard paramtrization) U iδ c12c13 s12c13 s13 cij = cosθij = s23c13 i, j = 1, 3 gnration nunbrs sij = sinθ ij c23c 13

20 if 3-family flavour at th strong mass hirarchy approximation m = m m m m δ m = m m m m m,m δm 2 L/E rgion whr m E / L causs oscillation and δm E / L g. 10 V atmosphric nutrinos -6 2.g. 10 V solar nutrinos (.g. atmosphric nutrinos m = 10 V, E = 1GV, L=1000km) P( α 2 ff sin 2θ αβ = 4 Uα3Uβ3 α3 β ) 4 U U sin (1.27 m E/ L) β α 2 m 2 δm 2 m Physics govrnd by: m 2 flavour contnts of 3 ffctiv 2-flavour lik oscillation 3 2 1

21 Effctiv 2-family atmosphric µ disapparanc in 3-family mixing sin 2θ = 4 U U = sin 2θ sin θ 2 ff µ µ sin 2θ = 4 U U = sin 2θ cos θ 2 ff µτ µ 3 τ E.Lisi, G.Fogli,... U small (ractors) < µ 3 τ3 2 2 µ 3 τ3 2 2 µ 3 τ3 4 U U 1 (full mixing atmosphric) U + U 1 U 0.1? U U 0.5? E.Lisi, Nutrino 2000

22 H.Sobl Nutrino2000 Spac is lft for U 2 3 0

23 Conclusions: No vidnc for disapparanc in LBL ractor xprimnts Ractor + Atmosphric nutrino xprimnts + in 3-flavour strong mass hirarchy modl room lft for a small contnts in 3 No mor constraining data to b xpctd from ractors in nar futur

24

25 Nutrino Oscillation Exprimnts at Low Enrgy Acclrators (Bam Stopprs) Sarch for µ oscillation at rathr larg m > ~ 0. 1V 2 2 Compar somhow conflicting rsults from two similar xprimnts: KARMEN2: no signal LSND: statistically significant signal LSND: G.Mills Nutrino 2000 KARMEN2: K.Eitl

26 Concptual dsign: shilding p 800 Mv π p targt dtctor 30 m <E > ~ 30 MV m 2 L E 1 V 2

27 Th Enrgy spctra from Dcays/Capturs at Rst from Dcays in Flight + + µ ( π µ µ ) + + µ ( µ ) + + µ ( µ µ ) µ oscillation µ π µ µ - ( ) LSNDnrgy spctra + + µ ( π µ µ ) µ oscillation µ ( µ N µ X) + + µ ( µ ) + + µ ( µ µ ) µ ( µ µ ) µ ( µ ) µ ( µ µ ) µ - ( ) π ( µ ) + + µ ( π ) + + ( π ) µ E < 53MV 53MV spctra ar for LSND 53MV µ E > 53MV

28 Dtctors vssl filld with oil + liquid scintillator dopd with nutronphag svral light signal by arrays of PMT s E =2.2MV γ H KARMEN2 Gd E γ =8MV E < thrsh E + Signal nuclar captur = 1.8 MV > 3 MV + p γ 's ( sc in tilla tio n γ ' s + - annihilation : 2 γ of kv Crnkov light + n E γ known) Spac and dlayd tim corrlation KARMEN2

29 Main Karmn2 pro: Tim structur of ISIS p sourc from π + and prompt + 20 ms from µ [ ] + µ background masurd in t,t ns signal from QE p from oscillation µ and from signal rcordd µ µ [ t + ns,t +. µ s] in with 2.2µ s slop cosmic background masurd [ t +. µ s,t + ms] in small duty cycl small cosmic background Sgmntd dtctor: bttr n- - spac corrlation High scintillator concntration: 4 bttr E rsolution

30 Main LSND pro: Elctron ID and dirction Homognous dtctor + low scintillator concntration Crnkov ring as + signatur 3 Mass L=18m (instad of 30m) lowr m 2 3% of DIF π + µ + µ (instad of 0.1%) highr nrgy bam componnt µ oscillation via C - N

31 LSND dtctor at LAMPF, Los Alamos KARMEN-II dtctor at ISIS, RAL

32 Statistical analysis difficultis KARMEN-2 no signal and vry low xpctd background : plac an Uppr Limit (for long: 0-vnt obsrvd sampl, 3 xpctd background) non physical max liklihood : sin 2 2θ < 0 LSND signal rgion in paramtr spac computd from rapidly oscillating liklihood function with many local maxima Profusion of rcnt paprs and workshops on our to fix C.L. limits from liklihood functions (starting G.J.Fldman & R.D.Cousins, Phys Rv D57(1998)3873)

33 KARMEN-2 rsults + + n n All backgrounds masurd xcpt intrinsic

34 KARMEN-2 xclusion plot sin 2θ < snsitivity = larg m L(sin 2θ, m ) 11 k= 1 = {r f (E,E,t, t, r) + osc osc promt dlayd prompt k (r = 1 r ) f (E,E,t, t, r) } back osc back promt dlayd prompt k P (r r ) xp oisson back back + Unifid frquntist approach (F.-C.)

35 Nw LSND global analysis of all vnt catgoris with a common Elctron triggr and E in [20-200] MV - triggr from µ dcay ( 2.2 µ s) β from N dcay (16 ms) GS γ from n captur (186 µ s) prompt β from N dcay (16 ms) GS γ from n captur (186 µ s)

36 Nw LSND global analysis of all vnt catgoris with a common Elctron triggr and E in [20-200] MV Global fit to all rlvant distributions E (,β,γ,µ) t( -β,γ,µ) r ( - β,γ,µ) θ ( - ) R : ratio of liklihood of prompt ( - ) and dlayd vnts (γ) to b corrlatd/accidntal for all lctron triggr vnts catgoris with paramtrs: π + /π production ratio all DAR and DIF π and µ fficincis µ,, β, γ Oscillation signal : γ vnts with larg R

37 Variabls ntring in R r ( - γ) t ( -γ) PMT hits E R for no-oscillation channl

38 Th oscillation signal in E in [20-60] MV Excss of vnts at R > 10 (larg -γ corrlation liklihood) bam on bam off xpctd xcss of total background background vnts ±9.2 Evnt xcss is E dpndnt R>10 L/E (m/mv) E (MV) Fit to full R distribution P osc =0.0025± ±0.0004

39 LSND signal rgion 2θ < sin. 3 snsitivity = Rlaxing cuts: - E in [20-200] MV - R>0 KARMEN2 larg m L(sin 2θ, m ) Nvnt {r f (E,R,L,cos θ ) + osc osc k k= 1 back = r f (E,R,L,cos θ ) } i i k i= 1 back xp N normal (ri N N i ) i= 1 + Cut at L= 2.3 (90%) 4.6 (99%) Compatibl & signals

40 Prliminary joind KARMEN2-LSND analysis Joind liklihood 3 snsibl common favourd rgions 90% 99% LSND alon KARMEN2, NOMAD,BUGEY xcludd K. Eitl hp-x and Nw J. Phys. 2 (2000)1

41 Conclusions LSND signal in m 2 ~ V 2 is on of th 3 oscillation signals No vidnc that rsult is wrong Allowd LSND paramtrs spac domain will not b fully covrd by KARMEN2 ( spring 2001): not nough statistics givn background Nd for a joind analysis basd on a common liklihood function basd on th final data, Nd nw xprimnt(s) with highr snsitivity: MiniBOONE approvd at FERMILAB from 2001 I216 proposal at CERN PS 2001

42 In th man tim ithr 3 m 2 µ τ s or A. D Rujula Nu2000

43 Th nutrino production chain (numbrs ar for LSND) 89% p+n 800 Mv 11% DAR 97% π + DIF 3% Absorbd 95% π - + µ µ DAR 100% µ + µ µ DAR 100% Absorbd 88% µ + + DIF 5% µ µ DAR 12% µ Sarch for oscillations µ + + from µ dcay s a t r st

44 Nutrino Oscillation Exprimnts at High Enrgy Acclrators CHORUS and NOMAD short baslin xprimnt Sarch for µ τ oscillation Motivation (arly 1990 s) τ apparanc in sam high nrgy τ fr µ bam at th CERN SPS Wid Band Nutrino Bam Sarch for hot dark mattr candidats with m > 1 V with ~50 tims bttr snsitivity than E531: P osc ( µ τ ) > 10-4

45 CERN Wid Enrgy-Band Nutrino Bam Lin µ µ τ Φrlativ < E > [GV] ~ ~ ~43 Irrducibl prompt τ background from D S τ τ lss than 0.1 vnt in 4 yars wll blow snsitivity Maximum 27 GV m 50 V 06. km 2 2

46 M. Mzztto Nutrino 2000 P.Astir at al. CERN-EP )

47 τ signal xtraction tchniqu: xcss of vnts in kinmatics box prcis nrgy/momntum & good particl ID

48 Dcay channls τ τ π τ 0 h(n ) τ τ π π π (nπ )τ 15.2% 17.% 8 small CC background 49 5% kinmatics vry Total 82. 5% Exampls of snsitiv kinmatics variabls NC Not usd τ µ µ τ hug CC background µ 17. 4%

49 τ signal xtraction tchniqu also rquirs Prcis simulation of kinmatics of signal and background In kinmatics box whr signal xpctd: background known to O (10-5 ) Data Simulator - Rplac µ in CC Data (DS) and MontCarlo (MCS) sampls by Mont-Carlo (backgound NC) τ µ (signal CC - (background CC ) τ ) ε S,B Data = ε s,b MC ε ε S,B DS S,B MCS Most systmatic (hadron showr simulation, Frmi motion, ) cancl out

50 Analysis tchniqu Evnt classification (signal/background) basd on log liklyhood ratio ln λ = LS(X i) ( L (X ) ) is th probability for an vnt dscribd by kinmatics X to b signal (background) X i choosn as most discriminating variabls L product of (quasi)indpndnt multivariat pdf ( X, X,...) B i i i j LS ln L B Tail of ln λ (larg signal, small background probs) dvidd into (indpndnt) signal bins Binning obtaind from maximum snsitivity (basd on MC à la Fldman-Cousins) Dcay channls and signal bins combind à la Fldman-Cousins (unifid frquntist approach) Blind analys is : data in potntial signal rgion not lookd at untill analysis fully dfind

51 - τ τ Signal rgion blindly slctd dividd in 6 bins Evnt slction: fficint - ID (20%) - /π - rjction ~ /π 0 rjction ~ 10 4 Background and γ from NC - isolation Background from CC (1.5% of CC µ ) Transvrs momntum imbalanc 6 vnts in bins of DATA box found aftr box dfinition

52 - 0 τ π h( n ) τ inclusiv (B.R.=49.5%) 0-γ sampl Vry nw vnt slction: h - slction sinc CERN-EP shown at Nu2000 π 0 liklihood (2 γ ) ρ liklihood (>1 γ ) h - candidat liklihood bttr - /µ rjction - and h - channls contribut similarly to snsitivity

53 Sarch Summary = xpctd numbr of signal vnts if P osc ( µ τ ) = 1 Channls/Bins with vry low background Evnts xpctd: 55.2±5.2 Evnts found: 58 N τ = 14937

54 Nw CHORUS (diffrnt statistical C.L. Unifid frquntist approach sin 2θ > for larg m µτ

55 Mor to xpct from NOMAD: µ τ and τ still bing improvd τ πππ channl µ in progrss τ talk by R.Ptti in PS6 Λ polarization in N µ ΛX µ talk by Minh-Tam Tran in PS6

56 CHORUS xprimnt Sarch for µ τ oscillation Collaboration Blgium (Brussls, Louvain-la-Nuv), CERN, Grmany (Brlin, Münstr), Isral (Haifa), Italy (Bari, Cagliari, Frrara, Napls, Rom, Salrno), Japan (Toho, Kinki, Aichi, Kob, Nagoya,Osaka, Utsunomiya), Kora (Gyongsang), Th Nthrlands (Amstrdam), Russia (Moscow), Turky (Adana, Ankara,Istanbul) L.Ludovicci Nutrino 2000 E.Eskut at al. CERN-EP ??)

57 τ Dirct dtction tchniqu Obsrvation of th τ-lpton track producd in CC τ intractions in 770 kg nuclar mulsion targt : kink topology µ h τ τ µ π π π ( nπ + 0) τ B.R. 18% 50% π 0 ( n ) 14% not yt includd Prompt τ background <~ 0.1 vnt in 4 yars τ τ = < βγcτ τ > 1.5 mm Kink

58 CHORUS targt trackrs mulsion stack 4 stacks of mulsion intrlavd with fibr trackrs and mulsion intrfac trackrs 1 stack : 142 x 144 x 2.8 cm 3 = 36 plats of 790 µm 1 plat MIP ~35 grains / 100 µm mulsion 350 µm bas 90 µm mulsion 350 µm 100 µm Grain siz ~ 1. µm Grain masurmnt ~ 0.3 µm Angular rsolution 1.5 mrad 80 µm

59 CHORUS dtctor : vnt kinmatics masurmnt µ - Spaghtti Calorimtr Emulsion targt Scintillating fibr trackr h- Hadron Sign and momntum Air-cor magnt hadron spctromtr p/p = ( p(gv/c) ) Showrs nrgy, missing P t Lad&fibrs spaghtti calorimtr E/E=32%/ E (hadrons) E/E=14%/ E (lctrons) q hadr ~60 GV Muon spctromtr Air cor magnt hadron spctromtr Vto plan Muon ID, sign and momntum Iron-cor muon spctromtr p/p~10%-15% (p<70 GV)

60 Automatic Emulsion Data Taking (K.Niwa and Nagoya Univrsity 16 S bam 100 µm 54 µm 21 µm 0 µm Viw siz: 30x40 mm 2 Focal dpth : ~3 mm

61 Analysis stratgy Evnt rconstruction and loos kinmatics slction µ τ µ h τ 0 (n π ) 1 µ with p µ <30 GV/c no µ and at last 1 h - with 1<p<20 GV/c σ = 150µ m pos σ = 2mrad θ Track prdictions at mulsion trackrs for tracks rconstructd in scintillating fibr trackrs Tracks found and followd by automatic microscops in 3 succssiv intrfac mulsion trackrs up to stack ntry Followd back plat by plat in targt to find vrtx Automatic sarch for a kink dcay topology: 3% of vnts Evnts with kink ar analysd manually: 1% of slctd vnts rtaind as candidats Prcis kinmatics analysis of candidats

62 Automatic Vrtx Location Follow-up track, plat by plat to th vrtx 100 µm most upstram of ach targt plat ar scannd Vrtx dfind by th first plat out of two conscutiv plats whr a track sgmnt is not found

63 Kink Finding - Parnt Sarch (Larg Angl-Long Path kinks) 100 µm most upstram of th vrtx plat ar sarchd for all track sgmnts in a con of width 1/P Sgmnts with small impact paramtrs w.r.t. th follow-up track Candidat track parnt track Manual microscop inspction (3% of scannd vnts) Manual candidat vnt slction: clan 1-prong kink: no sign of nuclar intraction 1% of inspctd vnts

64 Data Yar All POT / Good mulsion 97% 73% 100% 100% ~93% Expctd Ncc / Emulsion triggr / ,305 1µ to b scannd 66, , , , ,459 1µ scannd so far 88% 55% 81% 83% 77% 1µ vrtx location and kink sarch 20,400 21,610 41,558 52, ,357 0µ to b scannd 19,846 29,350 37,143 36, ,412 0µ scannd so far 60% 58% 79%* 67%* 67% 0µ vrtx location and kink sarch 3,024 4,424 8,704 7,054 23,206

65 Background valuation and rduction π and K dcays P t (daughtr-parnt) > 250 MV/c : rjct 100 % Charm background primary lpton not idntifid and, if D +, charg of scondary wrong D - producd by µ / bam componnt Whit kink hadron lastic scattring with no sign of nuclar activity badly known rat is masurd at larg distanc from vrtx numbr within τ - dcay path computd by MC WK Charm dcays and whit kinks rduction in th h- channl P h dpndnt τ candidat dcay path cut such that 80% of th tru τ ar rtaind P h Φ(τ-Hadron showr) in transvrs plan > 90 Cuts optimisd for maximum snsitivity without looking at data τ

66 Background - + D from / CC with primary / + µ µ missd D / / + - from µ CC with primary µ missd and wrong charg for dcay µ /h CC and NC associatd D / D missd and D µ / h + nutrals "Whit kinks" h lastic scattring with no nuclar activity Prompt bam τ from D S dcays 1µ 0µ ngligibl <

67 P = N / N osc max µτ τ τ CC µ,h σ max osc A τ τ i N τ (P µτ = 1 ) = BRi Ni < ε i CC τ >= + = σ A i= Rsults µ µ i branching Nb cross--sction location fficincy kink finding ratios vnts ratios ratios fficincy Channl Obsrvd Expctd background N max τ µ h Uppr limit on 90% C.L (T.Junk, NIM A434 (1999) 435) t = osc 4 P µτ <

68 2 2 m (V ) µ τ NOMAD CHORUS CHORUS (Fldman-Cousins) (Junk) (F.-C.) "to compar" snsitivity (F.C.) osc P τ sin 2 2 larg m m ( V 2 full mixing sin 2 2θ Junk Fldman_Cousins N τ N τ < xpctd 90% C.L. givn < obsrvd s talk by R.Ptti in PS6

69 2 2 m (V ) τ Thr ar 0.9% of vnts in th bam osc P < τ 4 sin 2 2θ

70 Mor to xpct from CHORUS: 2 yars Phas-2 analysis launchd Rach P osc < 10-4 Among othr things: - improvd kink (τ) finding fficincy - 3-hadron and - dcay channls in mulsion thanks to nw upgrad in automatic microscop tchnology 100,000 10,000 1,000 0,100 0,010 0,001 #frams/s Othr Physics *+ CHARM physics in mulsion (D s obsrvation publishd) and in calorimtr as targt (J/ ψ production submittd) Form factors + Tridnt ( µ µ ) production Sarch for havy nutral lptons...

71 1.5 mm th haystack all sgmnts Th Nt Scan 2sgmnts connctd 1.5 mm Ral Data not passing through th vnt small impact paramtr