HERA - Structure of Matter and QCD

Transcription

1 HERA - Structur of Mattr and QCD p Contnts 5 yar running of HERA and H/ZEUS Elctrowak rsults Structur of th proton Katsuo Tokushuku (KEK, ZEUS)

2 DESY/HERA HERA 99-7 H ZEUS HERA: (7.5GV lctron 9GVproton) th world largst lctron microscop

3 Rsolution ~( Wavlngth) - ~ h Q ( ) Q - i f Rsolvd dimnsion [fm]. Ruthrford Hofstadtr SLAC p nucli proton partons [m] -6 Progrss in acclrator nabls us to invstigat th smallr structur. HERA: (7.5GV lctron(positron) vs. 9 GV proton). CERN μ,ν N Q ma=s=4e E p ~GV.. No sub-parton structur down to.67-8 m (HERA-I/II rsult, prlim.) HERA 9 95 THERA -9 Yar cf. in th rst fram s=e M p In ordr to obtain th sam CMS nrgy as HERA in a fid targt primnt, it ruirs 54TV lctron bam.

4 A viw of th HERA ring tunnl 4 Proton ring Tunnl Construction startd in 984 Elctron ring

5 Eprimnts startd in 99 5

6 6 HERA History (99-7) 5 yars yar brak HERA-I 99- HERA-II -7 HERA will stop at th nd of Jun in 7

7 Nutral Currnt (NC) Chargd Currnt (CC) 7 Scattrd positron Positron Proton Jt Scattrd positron Jt Anti-nutrino positron 7GV γ Z uark (u,d,s,c..) Proton 9GV positron 7GV W d,s-uark Proton 9GV Scattrd uark (jt) u,c-uark (jt)

8 Introduction: Dp Inlastic Scattring 8 p 9GV p p k 7.5GV k Dscribd by kinmatic variabls Q γ rmnant jt W currnt jt Q =- photon virtuality = Q /p. Bjorkn y = p./p.k Inlasticity s=q y Y±=(±(-y) ) F L : Longitudinal Str. Ft. ( in QPM) F : Small at Q << M z F = (,Q ) f f (,Q ) : f uark distribution function

9 pqcd viw of F PDF dpnds on Q F = (,Q ) f f 9 d DGLAP volution (Dokshitzr, Gribov, Lipatov, Altarlli, Parisi) df α s ( Q ) dy = g, ln Q π y [ ( ) ( ) + ( ) ( )] P y y, Q P y g y Q F Q largr: high- and g ar split into low and g. splitting function (known from pqcd) P ( y) y (y-) P g ( y ) y (y-) ~ (+)

10 Kinmatical rgion for HERA structur function masurmnts Q (GV ) 4 ZEUS ZEUS (Prliminary) ZEUS BPT 997 ZEUS SVX 995 ordr highr rgion in Q, ordr lowr rgion in Wid (O( 6 )) span in Q : Prcis masurmnts for Q volution NMC BCDMS CCFR E665 Kinmatic limit y= - y=

11 Prdictions of F Gluck, Rya and Vogt pqcd : parton volution Early HERA data showd rapid incras of F at low. Prcis F dtrmination ( data sampls) Donnachi & Landshoff Hadronic : Rgg thory bhavior of γp total cross sction Fid targt data

12 Rsults of F Structur Function Strong ris of F as dcrass Soft sa of uarks in th proton Slop of ris gts stpr as Q gos up HERA F Q =.7 GV.5 GV 4.5 GV 6.5 GV 8.5 GV GV GV 5 GV 8 GV GV 7 GV 5 GV Good agrmnt with fidtargt primnts at middl -high m F 45 GV 6 GV 7 GV 9 GV Sa + valnc uarks GV 5 GV - - ZEUS NLO QCD fit tot. rror H 96/97 ZEUS 96/97 BCDMS E665 NMC - -

13 F for fid, as a function of Q At low, strong scaling violation is sn. Larg gluon dnsity + g splitting F incrass P g ( y) y (y-) At ~., approimat scaling. At highr, F dcrass as Q Quark radiats off gluon: g P ( y) m F -log () 5 4 HERA F =6.E-5 =. =.6 =.5 =.4 =.5 =.6 =.8 =. =. =. =.5 ZEUS NLO QCD fit =.8 =. tot. rror =. H 94- prlim. H 96/97 ZEUS 96/97 BCDMS E665 NMC =. =.5 =.8 Lin = rsult of QCD fit (comming slids) All data points wll dscribd. y (y-) =. =.8 =.5 =.4 = Q (GV )

14 Kinmatical rgion for HERA structur function masurmnts 4 s=q y Q (GV ) 4 ZEUS ZEUS (Prliminary) ZEUS BPT 997 ZEUS SVX 995 ordr highr rgion in Q, ordr lowr rgion in Wid (O( 6 )) span in Q : Prcis masurmnts for Q volution NMC BCDMS CCFR E665 Kinmatic limit y= - y=

15 γ Z v,a v,a d σ [ ] [ ] + = = Z Z Z Z Q Q P a v a v P a a Q F Q Q P a v a v P v v Q F ), ( ), ( } 4 { ), ( ), ( ), ( } ) )( ( { ), ( + M Q Q sin = P Z w z θ parity - parity +, sin W I a I v = = θ In SM, 5 { } { } [ ] 4 ) ( ) ( F y F y Q ddq d p + = ± m πα σ W ν { } { } [ ] ) ( ) ( F y F y Q M M G ddq d W W F CC p + + = ± m π σ

16 Masurmnts of NC/CC Cross sctions 6 HERA-I Final Rsults At high Q (Q ~M W,Z ), Chargd Currnt Nutral Currnt dσ dq σ NC ~ σ CC α ( Q + M ) Echang α NC ~α CC Elctrowak unification Good agrmnt with th SM Mw = 8. ±.(stat)±.(syst)±.(pdf) GV (from ZEUS p data) NC( + p) < NC( - p) γz intrfrnc CC( + p)<cc( - p) u,d-uark distribution in th proton

17 Sachs of BSM 7 softr scattring If th uark is not point-lik λ SCALAR LEPTOQUARKS WITH F= ( S, L ) - - EXCLUDED H CI L indir. limit Prliminary ZEUS limit H dirct limit ( - p) D limit Ecss in data ( + p) M LQ (GV) p p LQ g LQ p λ LQ Good agrmnt with th SM Quark Radius<.67-6 cm (prlim.) No signal for Lptouarks so far

18 HERA I II 8 Longitudinal polarization of lpton bam : Dirct EW snsitivity Sokolov-Trnov ffct Lpton bam has transvrs polarization + Spin rotator bfor/aftr th H/ZEUS/HERMES dtctors. Polarization build-up at HERA Luminosity Upgrad : High-Q ruirs larg luminosity Final focusing magnts in th dtctor ~4% on avrag

19 Chargd Currnt Scattring ± σ CC (pb) σ CC 8 6 Chargd Currnt p Scattring - p νx H Data 5 (prl.) H Data ZEUS Data 4-5(prl.) ZEUS Data p νx H Data ZEUS Data Lft handd lctron lctron nutrino (lft handd) Proton 8GV d s-uark W(lft handd) u,c-uark (Jt) 9 4 SM (H PDF ) Right handd lctron nutrino Proton 8GV Q > 4 GV y < P lft handd right handd Right handd lctron d s-uark W(right handd) u,c-uark (Jt) σ R =.±.8±.6 pb (H and ZEUS combind prliminary rsult) -> W R mass limit ~ GV Th first masurmnt of Lft/Right asymmtry in CC in this nrgy rgion.

20 Polarizd Nutral Currnt Cross sction (d σ/ddq ) / (d σ m /ddq ) Vry subtl ffct from g-z intrfrnc -> H+ZEUS combind rsults a) Pol=7% - L - R + R + L A A ± P R - P L σ σ p R ± p R HERA H+ZEUS Combind (prl.) ± - σ + σ ± L L ± p p 4 5 Q (GV ) A + A - H PDF ZEUS-JETS PDF - 4 Q (GV )

21 Masurmnt of -Z coupling u-uark d-uark Polarizd data improvs th vctor couplings. HERA-II data maks a significant impact on th uark couplings

22 d σ ± p ddq γz F F ( = F (, Q ) σ πα 4 Q = [{ + ( y ) } F m { ( y ) } F ] { v v P + ( v + a )( v + a ) PZ }[ (, Q ) + (, Q )] (,Q ) F (,Q )/ a P Z 4v ava PZ }[ (, Q ) (, Q )] = a [ - ] γz Z - - σ + F p p, Q ) = { aapz + = Q P In SM, v sin z sin θ + = I θ W w Q MZ a = I HERA cf. νp: F : valnc uark H+ZEUS Combind (prl.) Q =5 GV Quark-charg wightd valnc uark distribution p :F : charg-suar wightd d γz F = { H PDF ZEUS-JETS PDF v v.65 F γz. d u +, d }d = 5 =. ±.9 ±.8 consistnt with QCD fit :.6 ±. - -

23 PDF dtrmination from HERA A fit (almost) clusivly with HERA data Jts cross sctions gluon γchang sa scaling violation gluon Q (GV ) H ZEUS sa, gluon Fid Targt Eprimnts: CCFR, NMC, BCDMS, E665, SLAC y= (HERA s= GV) valnc QCD + EW physics Z chang sa + valnc valnc only W ± chang u or d uark Fid targt primnts Standard fits (a la CTEQ, MRST ) us data from various (fidtargt and collidr) primnts. Why HERA only fits? Singl Eprimnt: Wll known systmatic uncrtaintis including corrlation. Proton Only: No nuclar ffcts. Still w nd following information High Q : No Highr twist from th othr primnts: Strang uark information Ubar-dbar asymmtry

24 ~ σ.5 Q = GV Q = 5 GV Q = 5 GV Q = 45 GV PDF dtrmination from HERA Q ZEUS NC: high Q = 65 GV Q = 8 GV Q = GV =6.E-5 Q = 5 GV =. HERA F A fit (almost) clusivly with HERA data m -log () =.6 ZEUS NLO QCD fit Jts =.5 sa, gluon valnc 5 tot. rror QCD + EW physics =.4 =.5 5 H =.6 H 94- prlim. cross Z chang =.8 4 ZEUS H 96/97 Q = GV Q = GV Q = 5 GV Q = 8 GV.8 Fid Targt Eprimnts: =. ZEUS 96/97.6 sctions sa + valnc CCFR, NMC, BCDMS,.4 BCDMS ZEUS E665, SLAC =. gluon E665 valnc only. 4 Q = 8 GV γchang =. NMC W ± Q = 5 GV Q = 95 GV Q chang = GV Q - - = GV Q = GV.6 ZEUS NC (prl.) = p (4.7 pb ) sa ~577 data points.5 u or d uark ZEUS-pol (prl.) =.8. P = +..5 scaling - Fid targt violation =..6 Q = 7 GV primnts Q = GV Q = 5 GV =..4 gluon -. CC: high Q = = df [.4 ( =.8 ) ( ). ( ) ( )] α s ( Q ) dy = Standard fits (a la CTEQ, MRST ) + P y y, Q Pg y g y, Q d ln Q us data from various (fidtargt and collidr) primnts. Why HERA only fits? Q = 7 GV π y =.. Q = 95 GV Q = GV F Q (GV ) Jt y= (HERA s= GV) =.5 Singl Eprimnt: Wll known systmatic uncrtaintis including corrlation. NC: low Q p (78.8 pb ).6 ZEUS-pol (prl.) =.4 P Proton Only: No nuclar ffcts. Still w nd following information = f() = p High Q =.65 : No Highr twist p (-) p (+p. from 5 ) th at othr Q primnts: =Q Strang uark information Ubar-dbar asymmtry σ ~.5 =.8 Q (GV ) DGLAP uation ZEUS CC (prl.) 4

25 PDFs obtaind from th fits Gluon uncrtainty 5 ~GV As sn in th F ris at low-, many sa uarks. Gluons ar dominant at low- Gluon dnsity is dtrmind at ~ 5% lvl, in th LHC-Higgs rgion. H/ZEUS comparison: Rasonabl agrmnt btwn th primnt Th main diffrnc coms from Initial Paramtr Handling of sys. rrors Slction of low nrgy primnts

26 Simultanous traction of α s and PDF Scaling violation: F / lnq ~ α s g(,q ) Data at low allow disntangling corrlation of α s and g α s -fr fit givs: H+fid targt: α =.5 ±.7(p) +.9 s.5 (additionally ±.5 from rnormalization scal) ZEUS+fid targt: α s =.66 ±.49(p) ±.8(modl) (additionally ±.4 from rnormalization scal) ZEUS only: α s =.8 ±.8(p) ±.8(modl) (additionally ±.4 from rnormalization scal) (modl) Diffrnc in p. rror mainly from th tratmnt of systmatic rror and normalization of data points in th fitting procdur and rror propagation. th. uncrt. p. uncrt....4 α s (M Z ) Jt shaps in NC DIS ZEUS (DESY hp-/4565) Multi-jts in NC DIS ZEUS prl. (contributd papr to ICHEP4) Inclusiv jt cross sctions in γp ZEUS (Phys Ltt B 56 () 7) Subjt multiplicity in CC DIS ZEUS (Eur Phys Jour C () 49) Subjt multiplicity in NC DIS ZEUS (Phys Ltt B 558 () 4) NLO QCD fit ZEUS prl. (contributd papr to ICHEP4) NLO QCD fit ZEUS (Phys Rv D 67 () 7) Inclusiv jt cross sctions in NC DIS ZEUS (Phys Ltt B 547 () 64) Dijt cross sctions in NC DIS ZEUS (Phys Ltt B 57 () 7) World avrag (S. Bthk, hp-/47) Various α s masurmnts at HERA. : All consistnt -> Univrsality of QCD 6

27 Summary 7 HERA and ZEUS/H primnts Collidr = tndd rgion in Q and. High- Q NC and CC: lctrowak ffcts NC: ffct of Z chang (-Z coupling, valnc uark) CC: flavor-spcific (ss positiv and ngativ uarks diffrntly) Masurmnts with th polarizd lctron bam ar mor snsitiv to th EM paramtrs. F masurmnt and PDF dtrmination Vry stp ris of sa and gluon at low. pqcd (DGLAP) givs a fairly good dscription of th data for Q = ~ GV Proton PDF is dtrmind with HERA data. Gluon distribution is wll constraind.