Diffraction at HERA and the TEVATRON

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1 Diffraction at HERA and th TEVATRON Nicolò Cartiglia INFN Turin Lisbon, PIC2 Rrsnting th CDF, D, H1 and ZEUS collaborations 1. Dfinitions 2. Kinmatics and Exrimntal Signaturs 3. Modls: From Rgg thory to QCD 4. Partonic Contnt of th Pomron PrortisofF IP 2 (β,q2 ) HERA-TEVATRONDataandTstofFactorization 5. Vctor mson roduction: γ V- W,tdndncofthcrosssction SU(4)symmtryathighQ 2 6. Conclusions

2 HERA bams: ± 27.5 GV 82 GV - cntr of mass nrgy: s = 3 GV Two gnral uros dtctors, H1 and ZEUS,arlacdonthHERAring. TEVATRON bams: 9 GV 9 GV - cntr of mass nrgy: s = 18 GV Two gnral uros dtctors, CDF and D, arlacdonthteva- TRON ring.

3 WHY DIFFRACTION? bcaus POMERONS ar vrywhr!!! You can find omrons in: Total cross sction D Inlastic Scattring Btwn Jts Vctor mson roduction Rgg thory and Pur QCD Many confrncs

4 Diffractiv vnts ar dfind as thos vnts mdiatd by omron xchang but what is a Pomron? Evn if diffraction is rsonsibl for a larg art of th cross sction (lastic scattring), vrylittlisknownonthnaturof th omron. No quantum numbrs ar xchangd Low t final stats M x and M y ar indndnt raidity ga I) II) X a a a IP IP b b b b III) X a ln(s) IP b Y lnm 2 lnm 2 y y x Pomron xchang rrsnts a gnric trm for long rang QCD raction ndd to xlain th ris of th total cross sction

5 Exrimntal signatur: 1) Raidity ga: -Fora standard DISvnt: Dfin: η =-ln(tan(θ/2)) Enrgy flow Total sudoraidity: η tot ln( W2 m 2 ) Quark - rmnant: η ln( 1 x ) η θ Dtctor -1.5 Probability to hav a ga: ( η) η

6 -ForRggonorPomronxchang: Enrgy flow ga η IP, R Dtctor Raidity ga gnratd by th xchang: ( η) 2(α() 1) η omron xchang α() 1 ( η) ρ, a 2, f 2,ω xchang α().5 ( η) η π xchang α(). ( η) 2 η Diffractiv vnts ar thos which lad to a larg raidity ga in final stat has sac and ar not xonntially surssd as a function of ga width.

7 2) Lading roton in th final stat: dn dxl DIS IP R IP.5 1 xl High fraction of original longitudinal momntum: For omron xchang: x L = z z 1. For non omron xchang: x L = z z < 1. Low transvrs momntum: dn d 2 with b = 5-15 GV 2 b 2

8 Exrimntal signatur: How can w slct diffractiv vnts? Many ractions, mdiatd or not by omron, gnrat diffractiv-lik vnts: a) Singl diffraction b) Doubl diffraction c) Evnts with larg raidity ga d) Non-Pomron (Rggon) xchang a) c) γ * γ * M X IP b) d) γ * γ * IP M X R M X M N Th challng is to undrstand thir ovrlaing. Diffrnt mthods hav bn usd so far by th collaborations

9 Raidity Ga 2 W 2 Q q X (M ) X Largst Ga in Evnt t Y (M Y) H1, DO, CDF, and ZEUS us a slction mthod basd on a visibl ga of articl in sudoraidity. For xaml H1 uss th following mthod: Th largst raidity ga in th vnt dfins two systms, X and Y. Th Masss M x, M y ar comutd If: - x IP = M2 x+q 2 W 2 +Q 2 <.5 -M y < 1.6 GV th vnt is acctd in th saml. This slction is basd on th H1 dtctor ability of: -Masuringhadronicactivityutoη 3.4 x IP <.5 -Vtoingactivityinthrgion3.4 <η<7.5 M y < 1.6 GV

10 Lading Proton Mthod Th ZEUS and CDF collaborations hav a Lading Proton Sctromtr to dirctly masur th scattrd roton. LPS acctanc:.6 < x L < 1. and< 2 < 1GV 2 Rsolution: -.3 % on z - 3 % on S6 S5 VERTICAL BENDING Six dtctor stations along th bam: S1 S3 singl latral stations S4 S6 doubl vrtical stations S4 S2 Collctd Luminosity:.9 b 1 in b 1 in Installd LPS Triggr 4. b 1 in 1996 S1 Dtctor orations using Roman ots Six µstri silicon dtctors r ot -thrdiffrntstriorintations ( o, +45 o, 45 o ) itch: 115µm o 2µm ±45 o -cutouttofollowth1σ bam rofil

11 CDF roman ots Krstin g 4

12 Ln M 2 X METHOD Diffractiv saml/cross sction dfind as xcss contribution in th ln M 2 X distribution abov th xonntial fall-off of th non-diffractiv ak It follows from th dfinition of diffraction that: dn dm 2 X 1 M 2 x = dn d ln M 2 X =const whil for non-diffractiv scattring: dn d ln M 2 X thn: =x(b ln M 2 X ) (uncorrlatd articl mission) dn d ln M 2 X = D + c x(b ln M 2 X )

13 2agstoxlainhoDandCDFslctthirvnts

14 Modls of Diffraction: Rgg Thory π α(t) π n α() J Scattring is mdiatd by th xchang of a trajctory x: π π o n mdiatd by th ρ trajctory: ρ, a 2,g α() = intrct, α = slo Two main trajctoris can b idntifid: Pomron: α IP (t) =α IP ()+α t with α IP () 1.8, α.25 GV 2 Rggon: α R (t) =.5 + t If a raction is mdiatd by trajctory k: σ tot s α k() 1 Pomron: σ tot s.8 Rggon: σ tot s.5 σ l σ 2 tot s 2(α k() 1) Pomron: dσ l dt s.16 ρ a t α g

15 Diffraction and Total cross sction Th hadron-nuclon total cross sctions,, k ±,π ± tc. hav bn fit to a siml common xrssion: whr σ tot (h) =X s.8 + Y s.45 th first trm accounts for th incras of σ with nrgy omron xchang th scond trm accounts for th dcras of σ with nrgy rggon xchang At high nrgy th total cross sction is comltly dominatd by th scond trm, omron xchang. Th sam aramtrization fits also th total γ crosssctionathera

16 Modls of Diffraction: QCD insird Standard DIS: Infinit momntum fram Scal st by Q 2 F 2 (Q 2, x) arton dnsity Diffractiv DIS: Proton rst fram All nrgy carrid by hoton: E γ 5 4 TV. Th hoton fluctuats into a q q air (simlifid ictur!) ustram th roton targt and collass into th final stat wll aftr th intraction. lc kt m q z (1-z) IP Pomron = 2-gluons xchang fluctuation lngth: 1 l c = roton 2m x > 1fm bj r Radius of q q m q Mass of th gnratd quark k, z Transvrs and longitudinal momntum of th q qair r

17 Th scal of th intraction is a combination of k, z, Q 2, m q and can b xrssd as: 1 r 2 = k 2 Q 2 + M 2 x M 2 x + m 2 q Not: Thr ar slightly diffrnt vrsions of r availabl Small r = hard scal Larg r = soft scal If m q is larg charm roduction, th scal is hard vn at Q 2 =. σ(γ L ) is dominatd by larg k 2 σ(γ ) is dominatd by small k 2 For light quark roduction, th scal dnds on th combination of k 2 Q 2 : Larg k 2 Small k 2 hard scal at low Q2 hard scal at high Q2

18 Modls of Diffraction: imortant but no tim.. Soft Colour Intraction Flux rnormalization...

19 How do w gt to know a Pomron? Hard and soft scals in Diffraction W hav a roblm: Th larg majority of diffractiv vnts ar soft, i.. thy do not hav a hard scal in th intraction To study th artonic natur of diffraction w nd to isolat th subsaml of diffractiv vnts which has a hard scal. For xaml: Th total cross sction is a soft rocss, th scal is t Jt roduction in diffractiv vnts has a hard scal ( t ) Diffractiv DIS has a hard scal (Q 2 ), Diffractiv Havy Flavour has a hard scal (m q ), Diffractiv roduction of Vctor mson might hav a hard scal (m V ). To undrstand Diffraction it is nccssary to study both soft and hard vnts and th transition btwn th two rgims.

20 Diffractiv scattring is a tool to study th transition from soft scal ractions (total cross sction) tohardscalractions(?). Diffrnt final stats and/or Q 2 allow to ma this transition. soft scal hard scal Q, k, m, σ / σ L T larg Total cross sction? Diffraction at HERA, TEVATRON

21 Diffraction: Kinmatics HERA cas, but it works for TEVATRON too... On mor vrtx! To standard DIS variabls add: t =(P P ) 2 M 2 X =(q + IP) 2 Momntum transfr at th roton vrtx IP γ invariant mass squard β = Q 2 2(P P ) q = x x IP = Q 2 M 2 X +Q2 t MX 2 Q 2 >> 1 β., MX 2 << 1 β 1. Q 2 Two variabls dscrib th longitudinal momntum lost by th roton in th intraction: x IP = (P P ) q P q x L = z z = M2 X +Q2 t W 2 +Q 2 M 2 Calorimtr Proton sctromtr x L = 1 x IP 1.

22 Th Partonic Structur of th Pomron γ * F( β, 2 Q ) γ X 1 Xom M X X 1 Xom g F( β, M X 2 Q ) -Th Pomron Structur Function can b studid both in and collision using th sam tchniqus usd for th standard roton structur function -Isitrasonabltosuosthatthsam omron isrsnt in nd?

23 Th Partonic Structur of th Pomron Tst of Factorization: HERA vs TEVATRON, HARD vs SOFT scal 1 Xom γ * F( β, M X 2 Q ) F D(3) 2 (Q 2,β,x IP ) ( x 1 ) a F IP 2 (Q 2,β) IP 1 Xom g F( β, M X 2 Q ) -Th Pomron Structur Function can b studid both in and collision using th sam tchniqus usd for th standard roton structur function Factorization imlis: ( 1 x IP ) a F IP 2 (Q 2,β) omron flux omron structur function Th omron flux and Pomron structur function ar indindnt of scal and rojctil.

24 Dfin: Prortis of F IP 2 (Q 2,β) F IP 2 (Q 2,β)= x IP 1 max( ) x IP min x n F IP 2 (Q 2,β) dx IP IP -Infactorizablmodls: F IP 2 (Q 2,β) F IP 2 (Q 2,β) -Innon-factorizablmodls: 1 Xom F IP 2 (Q2,β) <F IP 2 (Q2,β)> ovr a givn x IP intrval γ * F( β, M X M Y 2 Q ) To accss th artonic structur of F IP 2 (Q2,β) svral mthods hav bn trid: QCD fit High jts Charm roduction Enrgy flow Chargd currnt xchang

25 QCD analysis of F IP 2 (Q 2,β) (H1) Considr light quark flavor singlt (u +ū + d + d + s + s) +gluon Paramtriz at Q 2 =2.5GV 2 : x i/ip f i (x i/ip )=A i x B i i/ip (1 x i/ip) C i Solv DGLAP volution quations to volv arton dnsitis to highr Q 2 and fit A i, B i, C i to data (i=singlt,gluon) Charm includd via hoton gluon fusion No momntum sum rul imosd H1 Prliminary 1994 a) QCD Fit b) QCD Fit Quarks Only, Q 2 =2.5 GV2 Considr two ossibilitis: χ 2 /ndf = 95.2/39 -OnlyquarksatQ 2 β =.4 -QuarkandgluonsatQ β =.1 Quarks + Gluons, Q 2 =2.5 GV2 χ 2 /ndf = 36.8/37.25 β =.4 β =.1 β =.2 β =.2 Scaling violation at high β imlis a strong gluon comonnt β =.4 β = β =.4 β = β =.9 β = Q 2 / GV Q 2 / GV 2

26 Phnomnological fit including mson and omron comonnts: F D(3) 2 = F2 IP (β,q 2 ) x a IP + C M F2 M (β,q 2 n ) x 2 IP +intrfrncwithhasanglof45 Fit F2 IP (β,q2 ), C M, a and n 2 assuming F2 M = F2 π (GRV) H1 Prliminary Q 2 =2.5 GV 2 β=.1 Q 2 =3.5 GV 2 β=.1 Q 2 =5 GV 2 β=.1 P D(3) x I F 2.1 Q 2 =2.5 GV 2 β=.4 Q 2 =3.5 GV 2 β=.4 Q 2 =5 GV 2 β=.4 Q 2 =8.5 GV 2 β=.4 Q 2 =12 GV 2 β=.4 Q 2 =2 GV 2 β=.4.1 Q 2 =2.5 GV 2 β=.1 Q 2 =3.5 GV 2 β=.1 Q 2 =5 GV 2 β=.1 Q 2 =8.5 GV 2 β=.1 Q 2 =12 GV 2 β=.1 Q 2 =2 GV 2 β=.1 Q 2 =35 GV 2 β=.1.1 Q 2 =2.5 GV 2 β=.2 Q 2 =3.5 GV 2 β=.2 Q 2 =5 GV 2 β=.2 Q 2 =8.5 GV 2 β=.2 Q 2 =12 GV 2 β=.2 Q 2 =2 GV 2 β=.2 Q 2 =35 GV 2 β=.2 Q 2 =65 GV 2 β=.2.1 Q 2 =3.5 GV 2 β=.4 Q 2 =5 GV 2 β=.4 Q 2 =8.5 GV 2 β=.4 Q 2 =12 GV 2 β=.4 Q 2 =2 GV 2 β=.4 Q 2 =35 GV 2 β=.4 Q 2 =65 GV 2 β=.4.1 Q 2 =3.5 GV 2 β=.65 Q 2 =5 GV 2 β=.65 Q 2 =8.5 GV 2 β=.65 Q 2 =12 GV 2 β=.65 Q 2 =2 GV 2 β=.65 Q 2 =35 GV 2 β=.65 Q 2 =65 GV 2 β=.65 a = 1.29 ±.3 n 2 =.3 ±.3 χ 2 /ndf =17/156.1 Q 2 =8.5 GV 2 β=.9 Q 2 =12 GV 2 β=.9 Q 2 =2 GV 2 β=.9 Q 2 =35 GV 2 β=.9 Q 2 =65 GV 2 β= x I P

27 two ags from royon royon f 2d 2.s

28 2-3 jt Production in Diffractiv Evnts Using th arton dnsitis from F IP 2 (Q 2,β), thcross sction for multi-jt diffractiv roduction can b rdictd. Rsults ar availabl for: N jt =2, 3 Q 2 =, 4 <Q 2 < 8 GV 2 abs(t) < 1 GV 2 x IP.5 Jt studis shd light on: Gluon contnt, via hoton-gluon fusion q q vs q qg Pomron configuration Univrsality of arton distribution...

29 Diffractiv Production of D Cross sction valuatd from dcay channl: Evnts r MV D + D π + slow (K π + )π + slow H1 Prliminary 1994 H1 Data Fit to data MC (RAPGAP + Ariadn) M / GV M = M(K π + π + slow ) M(K π + ) Rsults ar availabl for: 1.5 < t (D ) < 8 GV 1 <Q 2 < 45 GV 2 abs(η(d )) < 1.5 GV 2 x IP.15 Diffractiv charm roduction shds light on: Rol of gluons in diffraction Undrlying dynamics of havy flavour On charm has no wavfunction uncrtantis...

30 Enrgy flow in diffractiv scattring Quark Dominatd Gluon Dominatd γ * γ * q q q } ^ 2P T q g P P Quark dominatd structur - limitd P T wrt γ IP axis Gluon dominatd structur - mor nrgy flow in cntral rgion, larg P T tails, charm roduction, di jt roduction Rsults show: Excss of nrgy flow at η. ovr xctation of quark dominatd structur, Significant high 2 vnts, Evidnc of gluon radiation from thrust analysis.

31 Summary on F IP 2 (Q 2,β) Data favor a significant gluon comonnt in th Pomron: rsults from QCD fit, jt roduction,charm cross sction and hadronic nrgy flow suort this hyothsis Diffrncs btwn TEVATRON and HERA show factorization braking HERAand TEVATRONF 2 D and normalization, ar diffrnt both in sha HERA:DiffractivDIS=1%NonDiffractivDIS TEVATRON:DiffractivW, b bdijt =1%NonDiffractiv

32 Vctor Mson roduction: a uniqu tool to study soft-hard scal intractio VDM + Rgg thory: th γ Vtransitionhansbfor th intraction and thn th vctor mson scattrs hadronically with th roton QCD insird: th q q airintractswiththtargtfirstand thn th mson is formd Vctor Mson IP IP VDM works wll whn th scal is soft QCD works wll whn th scal is hard Th scal is st by a combination of Q 2,t,M 2 V : Q 2 =.2(M 2 V + Q2 + t ) th transition soft hard hysics can b stud- Changing Q 2,MV 2 id

33 Vctor Mson Production γ V whr V = ρ, φ, J/Ψ,ω,Ψ(2S),ρ Vctor mson roduction is charactrizd by vry littl activity in th dtctor and by th rsnc of 2-4 tracks in th tracking chambr. Th rocsss studid so far ar: Raction Q 2 =. Q 2 >. ρ π + π X X φ κ + κ X X J/Ψ µ + µ, + X X ω π + π π X Ψ(2S) π + π J/Ψ X ρ π + π π + π X Dtctor Dtctor Low Q 2 2 High Q Low W High W Gnral slction critria common to th analyzs ar: -Rightnumbroftracksforagivnraction -Enrgyclustrsinthcalorimtrmatchthtracks,witha maximum unmatchd nrgy of.5 1. GV -Wrangrducdto4-14GV.Forsmall(larg)Wvalus th tracks ar too forward (backward) to b masurd in th tracking chambr. For som analyzs, highr valus of W hav bn achivd using vnts with th vrtx dislacd in th forward dirction and/or using th calorimtr.

34 Most imortant sourcs of background ar: -Doubldissociationsubtractionforthmasurmntofth xclusiv cross sction. If th mass of th scattrd roton systm is small ( 1.6 GV for H1, 5 GV for ZEUS), it rmains undtctd and thrfor th vnt is includd in th saml. Th amount of background dnds crucially on: M y dσ dm 2 Y 1 M n Y Dtctor Dtctor with n 2.2 Th valu of n coms from CDF masurmnts and from th sha of th nrgy dositd in th calorimtr whn M Y is larg. Background: 1% H1 25% ZEUS (diffrnt forward acctanc) Elastic Inlastic with low M y Background!! M y Dtctor Inlastic with high M y -Nonrsonantcontribution -Triggrthrsholds -MontCarlouncrtaintis

35 Examls of Hard Scal Ractions: -ElasticJ/ψ roduction at Q 2 GV 2 -lightmsonatlargq 2 Dscribd by QCD modls with W γ dndnc could to th low-x bhavior of th roton gluon dnsity xg(x, Q 2 ) J/Ψ cas:(ryskin, 1993) IP as a gluon laddr σ [α s ( q 2 ) xg( x, q 2 )] 2,with q 2 = Q2 + m 2 J/ψ + t GV 2 x = Q2 + m 2 J/ψ + t Wγ 2 and corrctions J/ψ rlativistic wav function gluon k rscattring or absortion of c c Equivalnt calculation for ρ roduction at high Q 2 (Brodski t al.) Snsitivity to th gluon distribution and to th slo σ(v) vs. W γ

36 Examls of Soft Scal Ractions: -LightVctorMsonroductionatQ 2 =. VDM+Rgg rdictions incras of th slo aramtr b with rsct of lowr nrgy rsults (shrinkag): b(w γ )=b + 2α IPln(W 2 γ) dσ γ /d t [µb/gv 2 ] 1 1 ZEUS 1994 (a) γ ω dσ dt = A b t A =11.9 ± 2.3 ± 2.1 µb/gv 2 b =1.6 ± 1.1 ± 1.4 GV 2 b [GV -2 ] t [GV 2 ] 25 this analysis 2 low nrgy data 15 1 (b) Th lin is th Rgg dndnc b = b +2α IP ln W 2 γ (α IP =.25) Norm. fixd on th HERA oint W [GV] cross sction bhavior with W: σ γ V (W γ ) (α IP (t =)=1+ϵ =1.8 from fit) W4ϵ γ b(w γ ) W.22 γ

37 σ(γ V) vs W From σ(γ) tot ρ, ω and φ at Q 2 GV 2 Rgg: σ γ V (W γ ) W.22 γ

38 Larg Q 2 :rstorationofsu(4)symmtry According to SU(4), whn m 2 q << Q 2, th ratio among cross sctions should dnd only on th msons wavfunction: ρ : ω : φ : J/Ψ =[ 1 2 (uū+d d)] 2 :[ 1 2 (uū d d)] 2 :[s s] 2 :[c c] 2 = 9 : 1 : 2 : 8 QCD dynamics nhancmnt of φ and J/Ψ: ρ : ω : φ : J/Ψ = 9 :(1.8) :(2 1.2) :(8 3.5) At Q 2.GV 2,thissymmtryisbadlybroknbutthHERA data at larg Q 2 show a dramatic incras of both th φ and J/Ψ cross sction Excitd stats: σ(ρ ) σ(ρ) =.36 ±.7 ±.11 at Q2 =4-5GV 2 σ(ψ(2s)) σ(ψ) =.16 ±.6 at Q 2 =GV 2

39 Summary on Vctor mson roduction: AlargamountofdataisnowavailablfromHERA Light vctor msons at low Q 2 show a bhavior comatibl with VDM: -SlowrisofthcrosssctionwithW -Incrasof b comatiblwithshrinkag. Havy vctor msons or light vctor msons at high Q 2 show adiffrntbhavior: -FastrisofthcrosssctionwithWcomatiblwithth ris of F 2 -Lowr b valu(notforthj/ψ) -Indicationofshrinkag? -SU(4)flavorsymmtryrstord comatibl with both soft and hard rdic- - dσ 1/Q 4 5 dq 2 tions -Onstoflongitudinalhotonscomatiblwithbothsoft and hard rdictions. With incrasd statistics, vctor mson roduction can b a uniqu tool to dtrmin th gluon distribution in th roton

40 Summary and Outlook: AlargamountofdataisnowavailablfromHERAandTEVA- TRON -ExandndundrstandingofQCDdynamicsallowforrcis rdictions -Diffractionallowstomathtransitionfromnon-rturbativ to rturbativ rgims -Thidaof onomronfitsall hasbnrovnwrong: HERAand TEVATRONF 2 D and normalization, ar diffrnt both in sha HERA:DiffractivDIS=1%NonDiffractivDIS TEVATRON:DiffractivW, b b dijt=1%nondiffractiv TEVATRON data show factorization braking in vnt with gas and Doubl omron xchang -Vctormsonroductionisakytooltoundrstanddiffraction -Vryintrstingtoicsnotcovrdhr: DlyVirtualComtonScattring ProductionofLadingBaryons Shrinkag...noShrinkag... -Nwdatacomingsoon: H1,CDF,Dwillhavromanots, -EvnLHC,looking forward to th Somron and th omronino!

Electroweak studies and search for new phenomena at HERA

Electroweak studies and search for new phenomena at HERA Elctrowak studis and sarch for nw phnomna at HERA A.F.Żarncki Warsaw Univrsity for ZEUS A.F.Żarncki Elctrowak studis and sarch for nw phnomna at HERA p./25 Outlin Introduction HERA and xprimnts A.F.Żarncki