HERA Collider Physics

Transcription

1 HERA Collider Physics Summer Student Lectures August 22 Hans-Christian Schultz-Coulon Universität Dortmund [H Collaboration] [

2 Overview on topics covered (or touched) in this lecture A. Introduction Elastic en-scattering Inelastic Scattering Quark-Parton-Model Structure Functions B. HERA Experiments The HERA Collider H & ZEUS C. Proton Structure F 2 measurement Parton densities α s and the Gluon D. (Di)-Jet Production E. Photon Structure Scale Problem DGLAP & BFKL Concept of Photon Structure F. Diffraction Introduction Inclusive Diffraction Exclusive Final States G. Heavy Flavour Physics Quarkonia Production Open Charm & Bottom H. Electroweak Aspects ep Cross Section EW Unification PDFs at High x, Q 2 I. Searches Direct Searches Indirect Searches J. HERA II Upgrade Experimental Setup Physics Prospects not covered not covered

3 Elastic Scattering Cross Section e (k ) e + N e' + N' i dσ dω M if 2 ρf f phase space Fermi s Golden Rule e(k) Nucleus at rest q = k k' q = υ, q N(N ) M if M if = = M if ψ * f V( r)ψ i dτ e i q r V( r)d 3 r F( q) perturbing potential Form Factor [describes structure of target] Elastic scattering on a nucleus with charge distribution ρ( ): r dσ dω = F2 ( q) dσ dω Rutherford pointlike scattering (no spin) F( q) = ρ()e r i q r d 3 r

4 Form Factor Properties e (k ) A. Describes the difference between scattering on extended objects with respect to pointlike target B. For q also e -iqr and lim q F( q) = ρ( r)d 3 r = e(k) Probed Target q ~ /λ [Resolving Power] C. If /q ~ r, small changes of q imply large changes of e -iqr. D. For /q << r, i.e. qr >> the expression e -iqr oscillates fast. Hence lim F( q) q E. For a spherical charge distribution one gets F( q) = F( q 2 ) = --q 2 r 6 2 Determination of elastic form factor possible Elastic cross section vanishes [DIS-Region] Proton: r 2 Proton m 5 To resolve proton structure one needs Q 2 >>.4 GeV 2 HERA: max. Q 2 = 5 GeV 2 probing down to -8 m

5 Relation of ρ( r) and F( q) ρ(r) F(q 2 ) δ( r) 4π a 3 e ar 8π q a 2 h a 2 32 / a 2 r e 2π q 2 exp a 2 h R 3 θ( R r) 4π ( sinα αcosα) α 3 with α = fr ( ) e r R a

6 Nuclear Form Factors Experimental Results ~ 45 MeV e- From difference of position of minima 48 4 R Ca > R Ca Charge distribution of atomic nuclei

7 Elastic en-scattering e (k ) Fixed target experiment [Lab frame] q = k k' = υ, q with υ = E E ' e(k) Nucleus at rest γ Q 2 q 2 -- h λ 2 = Resolving power of the photon P = ( M i N, ) P f = ( M N + υ, q) Target stays intact (elastic scattering): cross section p f 2 M N 2 M N 2 = = = M N 2 ( + υ) 2 q 2 M N + 2M N υ + υ 2 q 2 Expect: narrow peak at x= υ = Q M N -Q 2 x = Q M N υ X

8 Fixed Target Experiments [Example: DESY Strahl 22] Electrons from DORIS Spectrometer T: Target Qx: Quadrupoles H: Collimator V: Collimator Mx: Dipoles C: Cherenkov Counter Sx: Scintillators

9 First DIS Result [DESY 968] d 2 σ de'dω [nb GeV - sr - ] E = M p E/[E(-cosθ)+M p ] E ~ 4.5 GeV using: Q 2 = 2EE (-cosθ) Q 2 = 2M p ν [and M p = GeV] E = 4.9 GeV θ = o E

10 Observed Cross Section dependence at lower x. [schematic diagram] Hofstatter experiment cross section 956 (e-he Scattering) Expected if proton consists out of quarks with effective mass m q = /3 M p x = Q M N υ

11 Naive QPM Model [Feynman 969] u flat, frozen Proton consists out of partons Interaction due to interaction of partons Hadronic structure defined by distribution of partons at any given time 2r p u P changes in number and momenta of partons should be small during time they are probed d x i P Σ x i = < x i < Infinite momentum frame: Proton is moving with infinite momentum; proton mass can be neglected. Partons frozen during interaction time Can be treated as free during short time of interaction Photon-Proton interactions can be expressed as sum of incoherent scattering from point-like partons Partons identified with Quarks

12 Electron DIS Kinematics k' = ( E', k' ) p k = ( E, k) Deep-Inelastic Scattering: Extra degree of freedom Relation between Q 2 and υ no longer valid P' q 2 Proton = = = = = = ( q+ xp) 2 2xPq Q 2 γ Q 2 = -(k k') 2 P= xp W 2 ( P+ q) 2 P 2 q Pq M P q P' q Q 2 + 2Pq x = Q Pq [Bjorken-x] elastic: M x = M p inelastic: M x = W W extra degree of freedom!! elastic: Q 2 = inelastic: 2Pq fixed target =2M P υ Q 2 = 2 2Pq + M P W 2

13 DIS Kinematics Summary of Relevant Kinematic Variables s = (k+p) 2 = 4E e E p Q 2 = -q 2 = (k-k ) 2 = 2E e E e (-cosθ e ) υ = q.p/m p υ max = s/(2m p ) y = (q.p)/(k.p) = υ/υ max x = Q 2 /(2q.p) W 2 = (p+q) 2 = M p - Q 2 + 2M p υ Centre-of-mass energy squared Negative squared four momentum transfer Energy transfer in proton rest frame Maximum energy transfer Fraction of energy transfer Bjorken scaling variable Invariant mass of total hadronic system k k' Q 2 =sxy At fixed s only two independent variables p = (E p,,,e p ) k = (E e,,,-e e ) k = (E e,,e e sinθ e,-e e cosθ e ) Q 2 xp P' q p

14 e Electron-Quark scattering (spinless case) q Structure Function F 2 γ e q dσ( eq) dq 2 = 4πα e 2 2 q 4 q Rutherford scattering on pointlike target dσ( ep) dq 2 xq(x) /3 4πα = [ 2e2 u + e2 d ] = q 4 Naive QPM x p = uud > x = /3 4πα q 4 With quark-quark interactions xq(x) dσ( ep) dq 2 = 4πα e 2 [ 2 q 4 u ux ( ) + e 2 d dx ( ) + ] = 4πα F ( x) q 4 x QPM: Structure Function F 2 independent of Q 2 /3 x

15 Scaling [SLAC 972] F 2 Q 2 [GeV 2 ]

16 Scaling Violations [99++] SLAC 972

17 DGLAP Evolution Intuitive picture

18 F 2 at Low Bjorken-x [Pre-HERA Knowledge] DGLAP: No prediction for the x-dependence of F 2 [except asymptotic behaviour] A. De Rujula et.al. 974 Measure!! Remark: Accessing low x offers possibility to determine g(x,q 2 ) [see later]

19 Selected List of Fixed Target Experiments [Pre-HERA] Experiment Year Reaction Beam Energy SLAC - MIT 968 ep, ed GeV CDHS, CHARM <984 ν µ Fe <26 GeV FMMF <988 ν µ <5 GeV CCFR ν µ Fe <6 GeV BCDMS µp, µd -28 GeV EMC <983 µp, µd <325 GeV NMC µp, µd 9-28 GeV E µp, µd 9-47 GeV Electron energy limited by synchrotron radiation Muon beam experiments Different processes Universality of parton density functions

20 Q Accessing Lower Bjorken-x HERA Experiments Fixed Target Experiments Q 2 =sxy access to highest Q 2 y = [HERA: s ~ 5 GeV 2 ] y = [Fixed Target: s < 3 GeV 2 ] Fixed Target: accessing lower x at fixed Q 2 needs higher s s = 2M p E e s = 5 GeV E e = 5 TeV ep-collider: - access to lowest x at very low Q x s = 4E p E e E e = 3 GeV E p = 9 GeV s = 5 GeV

21 The HERA Accelerator Complex e Halle Nord H e p 36m R=797m p Halle Ost HERMES NW e p HERA- Halle West N NO Halle West HERA-B HERA 36m Stadion Stellingen W Kältehalle PETRA Magnet- Testhalle H -Linac DESY II/III PIA + e -Linac e --linac O Trabrennbahn p e Proton ring: Energy*: 92 GeV Mag. Field: T Current: ~ ma * before 998: 82 GeV ZEUS Halle Süd SW Electron ring: Energy: 27.5 GeV Mag. Field:.64 T Current: ~ 4 ma General: Proton bypass SO Energy in cms: 38 GeV Circumference: 6.3 km BX rate:.4 MHz Lumi:.5. 3 cm -2 s -

22 View into the Tunnel

23 Luminosity Ṅ L σ N = σ L dt σ L : integrated Luminosity = N L Φ a N = a = n A a v a Φ a : flux n a : density of particle beam v a : velocity of beam particles Ṅ = Φ a N b σ b N : reaction rate N b : target particles within beam area σ b : effective area of one single scattering centre L = Φ a N b L : Luminosity Collider experiments: Φ a HERA: N x ~ A ~. mm 2 n ~ 2 f ~ 5 khz Ṅa N a n v U N a n f = = = A A A L f nn a N b nn f a N = = b A 4πσ x σ y L ~ 3 cm -2 s - N a : number of particles per bunch (beam A) N b : number of particles per bunch (beam B) U : circumference of ring n : number of bunches per beam v : velocity of beam particles f : revolution frequency A : beam cross-section σ x : standard deviation of beam profile in x σ y : standard deviation of beam profile in x

24 2m m Software :SDRC-IDEAS level VI.i Performed by : Carsten Hartmann Status : October 993

25 The H Detector Puddle Heinz : Beam pipe & magnets 2: Central tracking chambers 3: Forward tracking 4: Electromagn. calorimeter 5: Hadronic calorimeter 6 : Superconducting coil 7 : Compensating magnet (PreUpgr.) 8 : Helium cryogenics 9 : Muon chambers : Instrumented iron : Muon toroid magnet 2: Backward calorimeter (SpaCal) 3: Plug calorimeter 4: Concrete shielding 5: Liquid argon cryostat

26 H detector in parking position

27 H Collaboration

28 ZEUS Collaboration

29 Schematic View of H Forward Tracking Central Tracking System Silicon Detectors Digital Muon System e FPS FNC ToF ToF Lumi p Forward Muon System Toroid Solenoid Liquid Argon SpaCal

30 Large Q 2 range Precision QCD Test of DGLAP evolution Q 2 (GeV 2 ) HERA Kinematic Coverage H ZEUS CDF/D Inclusive jets η<.7 D Inclusive jets η<3 Fixed Target Experiments: CCFR, NMC, BCDMS, E665, SLAC Small x range High parton densities Novel quantum system Small Q 2 regime Non-perturbative QCD Confinement Large CMS energy Electroweak Physics Search for new phenomena x

31 Investigating the Structure of the Proton d 2 σ dxdq 2 4πα F ( x, Q 2 ) xq 4 2 F 2 describes dynamic structure of proton QPM: F 2 = 2 e q xq(x)

32 TEST Typical DIS-Event [as seen by the H detector] Calorimeter Scattered Quark Backward Electrons Forward ϑ Scattered Electron Q 2 Protons Trackers Q 2 = 4E e E e cos 2 (ϑ/2)

33 Neutral Current Cross Section dσ/dq 2 (pb/gev 2 ) - -2 ZEUS d 2 σ dq Q ZEUS (prel.) NC e + p DATA CTEQ5D NLO e + p -6 stat stat syst E p =92 GeV, s = 32 GeV Q 2 (GeV 2 )

34 Kinematic Reconstruction E e Electron θ' e δy e y δe ' e y e E' e θ j Proton Electron method: E j Q e 2 = 2E e E' e ( + cosθ' e ) E' y e e ( cosθ' e ) = E e x e Q2 e ( sy e ) = Hadron method: E y j ( cos θj) h = E e 2 2 E Q j ( sin θj) 2 h = ( y h ) δy e y [ ] δ E j ( cos θ j ) E j ( cos ) θ j 2 x h = Q h ( sy h )

35 Q 2 (GeV 2 ) Structure Function F 2 [Principle of Measurement] ZEUS > 25 Events > 65 Events > Events < Events Basic (simplified) Procedure: σ 4πα xq 4 F 2 κ and σ F 2 = = In reality much more difficult as acceptances, backgrounds, higher order corrections etc. have to be taken into account. N L N κl N: Number of events L : Luminosity y= y= - y= -2 2 Kinematic limit Q 2 =5 GeV x

36 F 2 (x) at Q 2 =5 GeV 2 MRS D,D - : Fit to fixed target data only Different assumptions on xg(x,q 2 ) MRS D - H '92 F 2.6 Q 2 =5 GeV 2.4 MRS D.2.8 HERA CTEQ5D MRST99 ZEUS 96/97 H 96/97 NMC, BCDMS, E Fixed Target x 2-3% Precision

37 F 2 (x,q 2 ): Present Status F 2 (x,q 2 ) = x 2 e q q (x,q 2 ) F em 2 +c i (x) H 96/97 H 94/ Prel. ZEUS 96/97 NMC, BCDMS, E665 ZEUS NLO QCD Fit (prel. 2) H NLO QCD Fit x= x= x= Q 2 (GeV 2 ) x=.65

38 ep Cross Section [low Q 2 approximation] d 2 σ dxdq 2 = y-dependence describes helicity structure of interaction e spin e M 2 Before d, d, = = Before J 2 d λλ', + cosθ * 4πα [ + ( y) 2 ] xq 4 2 F ( x, Q 2 ) q q q q y After e d After d e pq E p E e ( cosθ * ) = = = pk 2E p E e Proton y 2 F L ~ e ± e ± q F 2 ( x, Q 2 ) = x e 2 q qxq, 2 ( cosθ * ) M 2 + ( y) 2 Factorization into Hard Process (perturbative) Soft Process (non-perturbative) influence small related to gluon density [contribution high y] [LO: F L =] γ SF q [ ( ) + q( x, Q 2 )] Non-predictable Evolve according to DGLAP evolution Universal?! q

39 QCD Improved Parton Model F 2 ( x) = x e 2 q dξq( ξ)δ x ξ = x e 2 q qx ( ) q q ξp QPM QCD z = x/ξ F 2 x x ( ) e2 = q d ---- ξ ξ q ( ξ ) δ x -- α s x P ξ qq -- 2π ξ log Q x µ 2 ξp x k, k T σ γ q qg σ γ q qg µ : cutoff parameter α s P 2π qq ( z) µ 2 Q 2 dk T k T 2 α s P 2π qq ( z) log Q µ 2 qxq (, 2 ) = qx ( ) qxµ (, 2 ) = qx ( ) + + α s Q 2 log 2π µ 2 x α s µ 2 log 2π µ 2 x dz P z qq z dz P z qq z ( )q( x z) ( )q( x z) (A) (B) Splitting function: Probability to find quark with momentum fraction z of a parent quark having emitted a gluon with momentum (-z) qxq (, 2 ) = qxµ (, 2 ) + α s Q 2 log 2π µ 2 x dz P z qq z ( )q( x z) (A)-(B)

40 DGLAP Equations DGLAP: Dokshitzer, Gribov, Lipatov, Altarelli, Parisi DGLAP evolution equations arise from requirement that q(x,q 2 ) should not depend on the choice of scale µ: & qxq (, 2 ) qxµ (, 2 α ) s Q 2 dz = + log 2π P µ 2 z qq ( z)q( x z ) x dq( x, Q 2 ) dq x µ (, ) α d logµ 2 = s d logµ dz P 2π z qq ( z)q( x z) =! x dq( x, µ 2 ) d logµ 2 = α s 2π x From iteration dz P z qq ( z)q( x z, µ 2 ) Inclusion of higher order graphs necessitates inclusion of additional splittings z z [ z2 + ( z 2 )] PDFs ( z) z 6 z z z z ( z) z

41 Determination of PDFs fitting the F2 data Procedure: Assume parametric form of parton distribution functions at starting 2 scale Q ~ O( GeV 2 ). [# Parameters: O()] Fit all data by evolving the PDFs to higher Q 2 Parametric Forms: xg(x) = ax b (-x) c ζ(x) xu(x) = a x b (-x) c ξ(x)... e.g.: H ζ(x) = +d x +ex ZEUS ζ(x) = xq i ZEUS NLO-QCD Fit (Prel.) a s (M Z 2 ) =.8 total exp. error CTEQ 6M MRST2 xσ(.5) xg(.5) Q 2 = GeV 2 xd v xu v x

42 The Gluon Density Input: F 2 xg(x,q 2 ) Q 2 =2 GeV 2 Q 2 =2 GeV 2 H NLO-QCD Fit 2 xg=a.x b (-x) c (+d x+ex) [FFN heavy-quark scheme] total uncert. exp. uncert. q v valence quark densities [via fixed target data] Output: xg(x,q 2 ) α s =.5 ±.7 (exp) (model) ±.5 (scale) Q 2 =5 GeV X

43 The Gluon Density, LHC and the Higgs ~ GeV ~ TeV M 2 = x x 2 s =: τs H Gluon-Gluon Luminosity τdl = gxq (, 2 )g( τ x, Q 2 ) dx dτ τ x with Q 2 = τs [gg CMS-Energy]

44 xg(x,q 2 ) Comparison of Results [Uncertainties due to Choice of Parametric Forms] H: xg(x,q 2 ) xg = ax b ( x) c ( + d x+ ex) ZEUS: xg = ax b ( x) c Further investigation necessary needs independent data high statistics precision measurem Q 2 =2 GeV 2 Q 2 =5 GeV 2 Q 2 =2 GeV 2 H NLO-QCD Fit 2 xg=a.x b (-x) c (+d x+ex) [FFN heavy-quark scheme] total uncert. exp. uncert. ZEUS NLO-QCD Fit (Prel.) 2 xg=a.x b (-x) c [RT-VFN heavy-quark scheme] exp. uncert X

45 TEST rφ-view of dijet event Electron Dijet Production Proton g(x) Quark α s Quark Remnant

46 The Strong Coupling Constant [A Reminder].5 α s (Q).4 Theory Data Deep Inelastic Scattering e + e - Annihilation Hadron Collisions Heavy Quarkonia NLO NNLO Lattice α s Q 2 ( ) = α s ( µ 2 ) β α s ( µ 2 ) log Q µ 2 [Evolution equation].3.2 Confinement region Coupling. gets large QCD O(α4 s ) { 23 (5) Λ MS 25 MeV.25 MeV MeV α s (M Z ).53 α s Q 2 ( ) Asymptotic freedom Unique to non-abelian theories = β log Q Λ Fundamental QCD parameter Scale of process [Needs to be measured] Q [GeV]

47 electron Q 2 scattered electron jet Dijet Kinematics E t proton jet E t,jet2 Q 2 = 4 E e E e cos 2 (ϑ/2) remnant η jet scattered electron e 27.5 GeV Forward ϑ Backward 82 GeV p jet E t,jet

48 The Breit Frame Born process l l boson-gluon-fusion l l QCD-Compton Q 2 = -q 2 x Bj x Bj Q 2 M 2 JJ p p ξ Large E t only for O(α s ) Breit frame: 2x Bj P + q = p T Born process p z boson-gluon fusion

49 Inclusive Jet Cross Section d 2 σ jet / de T dq 2 / (pb/gev 3 ) 2 - inclusive jet cross section H data NLO CTEQ5M NLO (+δ hadr. ) Q 2 / GeV 2 [5... 2] ( 2) pert σ jet σ jet = = n α s n pert σ jet parton densities C in i= g, q, pdf i ( + δ hadr. corr. ) calculable incl. k algorithm [2... 3] ( 2) [3... 6] ( 2) [6... 5] E T,jet,Breit / GeV hadronisation corrections: <% Sensitivity on α s!!!

50 Determination of the strong coupling constant α s H α s from inclusive jet cross section for CTEQ5M parton densities 5 < Q 2 < 5 GeV 2 inclusive k algo. α s (E T ) α s (M Z ) µ r = E T World average α s (M Z ) =.86 ± exp. theo,.2. 2 E T / GeV PDF

51 The Gluon Density from 2-jets and charm xg(x,q 2 ) x g(x) 2 NLO QCD fit µ 2 f = 2 GeV 2 H jet data for α s (M z ) =.84 ± CTEQ5M MRST99 Botje Q 2 =2 GeV 2 µ 2 =25 GeV 2 2 incl. k algorithm -2 - x H prel. exp thy D* (DIS) D* (γp) x

52 Parton Ladders and Photon Structure

53 Electron Electron x small additional log /x terms breaking of k T -ordering Proton Proton Remnant

54 Forward Particle Production ZEUS 995 Backward high p t Forward 5 5 dσ/dx [nb] dσ π / dx / nb 4 2 Forward π production H data p* T,π > 2.5 GeV LEPTO 6.5 RAPGAP 2.6 mod. LO BFKL [ ] Q 2 / GeV 2 [ ] < E T/Q 2 < 2 Forward Jet Production 5 a) [ ] ZEUS Data RAPGAP, dir+res RAPGAP, dir LEPTO x DGLAP log /x Evol. γ-structure -3-2 x

55 Electron Electron Proton

56 σ γ*p (Q 2 ) / nb 4 4 < E t * < 5 GeV 3 2 H data LEPTO ARIADNE < E t * > 2 Q 2 / GeV 2

57 γ Direct x γ = 2 P t = Q 2 Photon Structure Nomenclature Proton γ Resolved Events Proton Remnant x γ P t 2 Proton Proton Remnant x γ

58 Can HERA measure γ F =x 2 γ e q γ (x,p ) q T 2 γp Dijet Cross Section 2? Sensitivity to xg γ

59 γp Dijet Cross Section e e ~ f p Proton ~ f γ γ Photon Remnant JET JET Proton Remnant dσ / dlog(x γ,jets ) [nb] E T,Jet > 6 GeV H data PHOJET (GRV) PYTHIA (GRV).2. gluons quarks direct γ Photon Flux Effective Parton Density of Proton Measure! Matrix Element - x γ,jets

60 Extraction of the effective parton density of the photon ~ α - x γ f γ, eff F γ 2 (Q 2,udsc) / α OPAL (. < x <.6) TOPAZ (.3 < x <.8) AMY (.3 < x <.8) ALEPH prel. (.3 < x <.8) JADE (. < x <.) L3 prel. (.3 < x <.8) DELPHI prel. (.3 < x <.8) γ TPC (.3 < x <.6) H f eff (.4 < x <.7) GRV LO (. < x <.6) p T 2 [GeV 2 ] /α x γ f eff γ H Data GRV 92 quark/antiquark contribution Gluons GRV LO (.2 < x <.9) GRV LO (.3 < x <.8) SaSD (. < x <.6) HO (. < x <.6) ASYM (. < x <.6) 2 3 γ 2 ~ x=.5 F 2 = <e q > f γ Q 2 [GeV 2 ] as gluon contribution small at large x Quarks - x γ

61 F 2 γ Structure Function F 2 of the Photon x x 2 + [ x] 2 / α F 2 γ F 2 γ = F 2 γ,qed (x,p2 ) Q 2 = 5.4 GeV 2 P 2 =. GeV 2 P 2 =. GeV 2 P 2 =.5 GeV 2 P 2 =. GeV 2 P 2 =. GeV x

62 Gluon Density of the Photon 2 P T = 74 GeV 2 ~ f γ = q(x γ,p 2 )+9 2 / T 4 g(x γ,p T ) α - x γ g(x γ ) H jet data, 996 H single particles, 994 GRV 92 GRS 99 SaSD LAC Known [e.g. from LEP] HERA 3 2 Observation of low x - x γ

63 Virtual γ Structure: Dijet x-section Study region Q 2 < E t 2 x γ =: direct x γ <: resolved E t x γ Dijet System direct γ contribution too small resolved γ component needed x γ

64 Diffraction

65 Hadron-Hadron Scattering Total x-sec σ tot Regge-Theory: σ tot ~ (W 2 ).8 pp Optical Theorem: pp [forward] γp HERA: Q 2 ~ [quasi-real γ s] γγ W

66 Incoming Electron Colour Field Diffractive Signature Standard DIS Incoming Electron Incoming Proton Diffr. Signature No Colour Flow P Incoming Proton Events 5 4 ZEUS 994 data Pompyt DIFF MC Ariadne DIS MC Rapidity Gap 3 2 Diffractive Events η max = ln tan(ϑ min /2)

67 Diffractive Cross Section d 2 σ dxdq 2 = 2πα [ + ( y) 2 ] F xq 4 2 ( x, Q 2 ) Structure of the proton d 3 σ D dx P dβdq2 = 2πα ( y) 2 D3 [ + ] F βq 4 2 ( ) ( β, Q 2, ) x P Structure of the Pomeron [+ Pomeron flux]

68 F 2 D(3) Q 2 Deviation due to meson exchange ( R-Exchange) [at large x P ] H 994 Data β Q 2 =4.5 GeV 2 Q 2 =4.5 GeV 2 Q 2 =4.5 GeV 2 Q 2 =4.5 GeV 2 Q 2 =4.5 GeV 2 Q 2 =4.5 GeV 2 β=.4 β=. β=.2 β=.4 β=.65 β=.9 Q 2 =7.5 GeV 2 Q 2 =7.5 GeV 2 Q 2 =7.5 GeV 2 Q 2 =7.5 GeV 2 Q 2 =7.5 GeV 2 Q 2 =7.5 GeV 2 β=.4 β=. β=.2 β=.4 β=.65 β=.9 Q 2 =9 GeV 2 Q 2 =9 GeV 2 Q 2 =9 GeV 2 Q 2 =9 GeV 2 Q 2 =9 GeV 2 Q 2 =9 GeV 2 β=.4 β=. β=.2 β=.4 β=.65 β=.9 Q 2 =2 GeV 2 Q 2 =2 GeV 2 Q 2 =2 GeV 2 Q 2 =2 GeV 2 Q 2 =2 GeV 2 Q 2 =2 GeV 2 β=.4 β=. β=.2 β=.4 β=.65 β=.9 Q 2 =8 GeV 2 Q 2 =8 GeV 2 Q 2 =8 GeV 2 Q 2 =8 GeV 2 Q 2 =8 GeV 2 Q 2 =8 GeV 2 β=.4 β=. β=.2 β=.4 β=.65 β=.9 Q 2 =28 GeV 2 Q 2 =28 GeV 2 Q 2 =28 GeV 2 Q 2 =28 GeV 2 Q 2 =28 GeV 2 Q 2 =28 GeV 2 β=.4 β=. β=.2 β=.4 β=.65 β=.9 Q 2 =45 GeV 2 Q 2 =45 GeV 2 Q 2 =45 GeV 2 Q 2 =45 GeV 2 Q 2 =45 GeV 2 Q 2 =45 GeV 2 β=.4 β=. β=.2 β=.4 β=.65 β=.9 IP+ IR IP only Q 2 =75 GeV 2 β= D3 F ( ) 2 = f x P p P Q 2 =75 GeV 2 β= ( )F P 2 β, Q 2 F P 2 ( β, Q 2 ) Q 2 =75 GeV 2 β= Q 2 =75 GeV 2 β= ( ) + f R x p P Q 2 =75 GeV 2 β= x I P ( )F R 2 β, Q 2 ( ) D3 ( ) = x F 2 [for small x] P Characteristic / -Dep. x P [Regge-Theo.] [exp. proven ]

69 Partonic Structure of the Pomeron F 2 P.3.2 NMC BCDMS SLAC H Preliminary NLO QCD Fit x=.4 F 2 P.5 H 994 H Preliminary 995 x IP =.5. β =..5.5 β =.4 β = Q 2 / GeV β =.2 β =.4 β =.65 β =.9 Different behaviour compared to proton Rises also for large parton momenta 2 Q 2 (GeV 2 )

70 Parton Content of the Pomeron z f(z).5.5 (a) Q 2 =4.5 GeV 2 Gluon Light Quarks H H 994 Result Uncertainty? DGLAP Gluon: Q 2 =4.5 GeV 2 Q 2 =4.5 GeV (b) Q 2 =2 GeV 2 (c) Q 2 =75 GeV z z β

71 New NLO Fit [to new (997) diffractive data] H preliminary H 22 σ r D NLO QCD Fit z Σ(z,Q 2 ).2. Singlet z g(z,q 2 ) Gluon Q 2 [GeV 2 ] 6.5 (exp. error) (exp.+theor. error) H 22 σ r D LO QCD Fit z z 5 9 dz z g(z,q 2 ) / dz z [Σ+g](z,Q 2 ) H preliminary Gluon Momentum Fraction for.<z< H 22 σ r D NLO QCD Fit (exp. error) (exp.+theor. error) 2 Q 2 [GeV 2 ]

72 Study of Hadronic Final States in diffractive events Gluon dominated P* T large (GeV -2 ) /N dn/dp T *2 - Gluon dominated.2 < X F <.4 H 994 DATA M X = 2 GeV EMC W = 4 GeV RG-F D 2 (fit 3) RG-F D 2 (fit ) LEPTO 6.5 γ * P Quark dominated -2 Quark dominated γp Proton p T *2 (GeV 2 )

73 Physics at High Q 2 Electroweak Aspects PDFs at High x,q 2 Searches HERA II Upgrade

74 rφ view NC DIS Event [as seen in a typical HERA detector] Q 2 = 695 GeV 2 Protons Electrons rz view

75 Neutral Current Interactions σ e e e e γ q e q q + ξ e ξ q Z q q q q Q 2 Q M Z 2 = Q 4 Q Q M Z Q M 2 Z with: ξ e = v e +λa e ξ q = v q +λa q λ = ± (Helicity) = κ Σ e Q 4 q2 qx ( ) κ Σ e Q 2 Q 2 2 q ξ e ξ q qx ( ) + + M Z κ Σ ξ Q 2 2 ( + M Z ) 2 e2 ξ q2 qx ( )

76 [Polarized] Cross Section Expression ± d 2 σ NC ( e LR, ) dxdq 2 = 2πα Y xq 4 + F 2 LR, LR, + Y xf 3 Different sign for positrons and electrons ~ y 2 LR, F L { Y ± = ( ± ( y) 2 )} Helicity Structure LR, F 2 LR, xf 3 = = i x q i ( x, Q 2 ) q i ( x, Q 2 LR, [ + )] A q i x q i ( x, Q 2 ) q i ( x, Q 2 LR, [ )] B q LR, A q LR, B q = = e q 2 2e q ( v e ± a e )v q χ Z ( v e ± a e ) ( v q + a q )( χ Z ) 2 2Q q ( v e ± a e )a q χ Z + 2v ( e ± a e ) 2 v q a q ( χ Z ) 2 Propagator: Q 2 χ Z Q M Z Pure Photon exchange γz-interference Pure Z exchange

77 dσ/dq 2 (pb/gev 2 ) - ~Q -4 H e + p 94- prelim. H e - p ZEUS e + p 99- prelim. ZEUS e - p prelim. Neutral Current DIS Cross Section SM e + p (CTEQ5D) SM e - p (CTEQ5D) due to γz-interference -6-7 y < Q 2 (GeV 2 )

78 H e p ZEUS e - p prelim. H e + p 94- prelim. ZEUS e + p 99- prelim. σ NC 5 SM e p (CTEQ5D) SM e + p (CTEQ5D) NC reduced Cross Section 4 x=.8 (x) 3 2 x=.3 (x25) x=.8 (x5) x=.25 (x) ± σ NC --- Y + ± σ NC xq d 2 σ NC e ± ( ) 2πα 2 dxdq 2 = F 2 + f( y)f 3 + gy ( )F L x=.4 (x5) - -2 x=.65 Extraction of: ~ xf 3 (@ large Q 2 ) quark densities Q 2 (GeV 2 )

79 ± d 2 σ NC ( e LR, ) dxdq 2 = 2πα Y xq 4 + F 2 LR, LR, + Y xf 3 e ± e± γ,z q q Proton SF LR, F 2 LR, xf 3 = = i x q i ( x, Q 2 ) q i ( x, Q 2 LR, [ + )] A q i x q i ( x, Q 2 ) q i ( x, Q 2 LR, [ )] B q Proton structure [fitted in NLO] Hard process [electroweak couplings & propagator]

80 ~ xf 3 Extraction Method [Using NC e + p and e - p cross section] σ NC e ( ) σ NC e + ( ) = = ---- [ Y Y + F 2 + Y xf 3 ] [ Y Y + F 2 Y xf 3 ] + xf 3 = Y [ σ NC ( e ) σ NC ( e + )] 2Y sensitivity to valence quark densities xf 3 q x, Q 2 q xq, 2 sensitive high Q 2 where γz interference is sizeable additional factor needed if e + p and e - p data taken at different beam energies

81 xf Q 2 =5 GeV 2 H ZEUS prel. Q 2 =3 GeV 2 H 97 PDF Fit ~ xf 3 xf Q 2 =5 GeV 2 Q 2 =8 GeV 2 rises with Q 2 (@ fixed x) due to propagator χ Z = s W cw Q Q M Z xf 3.4 Q 2 =2 GeV 2 Q 2 =3 GeV 2 agreement of data with prediction from QCD fit x contribution ~ x to xf 3 : <3% xf 3 = Q e a e { 2Q q a q xq [ i qi] } χ Z + 2v e a e { 2v q a q xq [ i q i ]} ( χ Z ) 2 γz xf 3 Q e a e { xf 3 } χ Z

82 xf 3 γz 2 H Data Q 2 =5 GeV 2 Q 2 =5 GeV 2 Q 2 =2 GeV 2 H 97 PDF Fit xf 3 γz Q 2 dependence (from scaling violation) expected to be small direct comparison of measurements at different Q 2 possible x 5 = 2Q q a q [ q i q i ] = 2Q u a u N u + 2Q d a d N d = -- ( α 3 s /π) γz F 3 [sum rule a la Gross Llewellyn-Smith] H measurement: H QCD Fit:.65 γz F γz F 3.2 =.88 ±.44 =. agreement within 2 standard deviations

83 Titel rz view Protons Electrons rφ view CC DIS Event

84 Charged Current Cross Section e - (e + ) _ ν(ν) e - e - e + e + + u d + ν + d u + ν + d u + ν + u d + ν Proton W -(+) u-type (d-type) d-type (u-type) SF d 2 σ CC ( e ) dxdq 2 = πα s W [ u+ c ( y) 2 ( d + s) ] Q 2 2 ( + M W ) 2 Probes u-quark density d 2 σ CC ( e + ) dxdq 2 = πα s W [ u + c ( y) 2 ( d + s) ] Q 2 2 ( + M W ) 2 Probes d-quark density

85 ~ G F [constant] dσ/dq 2 (pb/gev 2 ) HERA Charged Current Cross Section H e + p 94- prelim. H e - p ZEUS e + p 99- prelim. ZEUS e - p prelim. SM e + p (CTEQ5D) SM e - p (CTEQ5D) ~ Q -4-7 y< Q 2 (GeV 2 )

86 H CC (Preliminary) s=32gev e p e + p 94- combined H 97 PDF Fit xu (-y) 2 xd σ CC.5 Reduced CC Cross Section σ CC.5.5 Q 2 = GeV 2 2 Q 2 =3 GeV 2 Q 2 =5 GeV 2 Q 2 =2 GeV 2 Q 2 =3 GeV ± 4s W ( Q + M W ) 2 σ CC = σ CC + σ CC πα 2 d 2 σ CC ( e ± ) dxdq 2 = x u+ c + ( y) 2 ( d+ s) = x[ u + c + ( y) 2 ( d+ s) ].5 σ CC.8 Q 2 =5 GeV 2 Q 2 =8 GeV 2 Q 2 =5 GeV Sensitivity to u,d quark densities

87 Knowledge of d/u Ratio M.Botje Fit to HERA ep data [H 994, ZEUS 994] Fixed Target proton and deuteron data [E665, NMC, BCDMS, SLAC] Neutrino data [CCFR] Drell-Yan data [E866] Constrained by W-Asymmetry DIS data Constrained by DIS data only Large uncertainty at high x [dependence on parameterisation] [e.g. due to nuclear corrections] Can be further constrained with NC and CC HERA data.

88 xu v.8 Valence Quark Distribution x=.25 H Preliminary xd v high x xu v xu v x=.4 x= Q 2 (GeV 2 ) xd v x= H 94- combined Q 2 (GeV 2 ) NLO QCD Fit: H only H 97 PDF Fit CTEQ5M MRST NLO QCD fit using high Q 2, neutral/charged current, e + p and e - p data. Quark densities determined via local extraction method for data points where the xq v contribution is >7%. xq xq v = σ v meas σ More statistics needed to constrain behaviour of d v, u v further. fit

89 9 LHC parton kinematics 8 x,2 = (M/4 TeV) exp( ±y) Q = M M = TeV 7 6 M = TeV LHC Q 2 (GeV 2 ) M = GeV + high x, high Q 2 Fixed Target 2 y = M = GeV 6 Test of QCD evolution over 4 order of magnitude. HERA fixed target important for LHC and e.g. the prediction of Higgs/W cross sections x

90 ZEUS Microvertex Detector HERA Upgrade ZEUS: Lumi System Triggering Microvertex Forw. Tracking H: Lumi System Triggering Fwd/Bwd Silicon Forw. Tracking

91 HERA I HERA II HERA I Luminosity Intergrated Luminosity (/pb) 5 e E P = 92 GeV E P = 82 GeV e H Days of Running HERA I e + p Scattering: L ~ pb - e - p Scattering: L ~ 5 pb - HERA II Year Int. Lumi 22 2 pb pb pb pb pb - Σ pb -?

92 Polarization for H and ZEUS Spin Rotator (exists) HERMES utilises Compton scattering measures energy weighted asymmetry Laser LPOL Polarimeter Spin Rotator (new) H Spin Rotator (new) Laser Goal: <2% accuracy per bunch per minute ZEUS TPOL Polarimeter utilises Compton scattering measures spatial asymmetry HERA B electrons

93 (d 2 σ/dxdq 2 ) / (d 2 σ em /dxdq 2 ) NC e - L e - R e + R e + L Q 2 (GeV 2 ) Polarisation Utilising Exploit sensitivity to EW couplings at high Q 2 σ obs (P) / pb ± σ CC = ( ± P)σ CC, P= ( ) +: Probe d v quark distribution (P= +) -: Probe u v quark distribution (P= -) ± e - p νx [Q 2 > GeV 2 ] ± σ NC ± σ NC = = ± σ NC, + ± Pσ NC, P f( qqew,, couplings) Four independent equations one each for Q e = ± and P= ±. 2 CC Possibility to Polarisation Disentangle individual quark densities Measure EW couplings v u, v d, a u, a d

94 EW Couplings v u,a u.22 LEP 22 Preliminary 4 x 25 pb - [Q e =±, P=±].2 HERA II P=.5 v c (v u ).8 σ SM HERA: Complementary measurement [HERA: u,d quark couplings] [LEP: c,b quark couplings] Precision compatible with LEP results %CL a c (a u )

95 Searches at HERA electron (e ± ) Search for non-standard topologies? proton q,γ?? Topics: Lepton Flavour Violation Leptoquark Searches Excited Fermions remnant R-Parity Violating SUSY Quark Sub-structure Competition between HERA and Tevatron [... but HERA will search uncovered phase space in many channels]

96 Searches Examples [ Open windows for discoveries? ] Leptoquarks: e ± q e ± q [Signature: high Q 2 ] R p -violating SUSY: e + d stop [Signature: Isolated leptons & missing p t ] ~ t b ~ Doubly charged Higgs: e + γ e - H ++ [Signature: 3-Lepton events]

97 Leptoquark Search Mass Spectrum Events 3 2 H data SM with uncertainty Events 2 H data SM with uncertainty H PRELIMINARY e + p e + X Mass (GeV) H PRELIMINARY e + p ν X Mass (GeV) M LQ = (k+xp) 2 = xs [since s = 4E e E p ] xp k

98 Leptoquark Search Branching Ratio LQ eq β e Present Status D Run I H Preliminary e + p β e Future Sensitivity TEVATRON : L.5 fb - HERA 4 pb - HERA 8 pb λ=.3 λ=.5 λ=. λ= M LQ (GeV).3.2. HERA : λ =.5 (eu - LQ) M LQ (GeV) HERA will provide best limits for low branching ratios

99 High P t Leptons with missing Transverse Momentum P t,miss = 43.5 GeV M T(µν) = 22.6 GeV P t,µ = 27.7 GeV Clear Signature!... the story continues

100 High pt Leptons P t X vs. M T High p t µ and e H preliminary [.6 pb - ; 94- e + p data] H: 8 events seen; approx. expected p t X >25 GeV: events seen; approx. 3 expected ZEUS: P X T (GeV) L MC = 5. L Data P X T (GeV) H good agreement with expectation Explanation: 2 2 statistical fluctuation or new signal. 2 M eν T (GeV) 2 M µν T (GeV) Needs more statistics...

101 Electron Pair Production M 2 = 3 GeV Multi-Electron Event P t =63GeV P t =62GeV Selection: 2 electrons with (2) P t > GeV (5 GeV) [with 2 o < θ < 5 o ] 3rd electron with E 3 > 5 GeV ( GeV) [with 5 o < θ < 75 o ] Observation of 6 events with M 2 > GeV

102 Multi-Electron Analysis Events 6 4 H Preliminary H Data 5 pb - 2e GRAPE NC-DIS +Compton Events 2 2e Events 2 2e 2-5 E-P z (GeV) -2 2 miss (GeV) P T P hadrons (GeV) T Events 2 3e Events 3e Events 3e - 5 E-P z (GeV) -2 2 P miss (GeV) T P hadrons (GeV) T Good overall description of data by MC prediction

103 Multi-Electron Analysis Events 2 H Preliminary H Data 5 pb - GRAPE NC-DIS 2e +Compton P T e+p T e2 (GeV) 5 2e L MC(GRAPE) 5 L DATA M 2 > GeV H Prel. Data SM 2e 3.25±.5 3e 3.23±.4-5 high M ee > GeV M 2 (GeV) 5 5 M 2 (GeV) Note: Different topology of 2e and 3e events Events - 3e P T e+p T e2 (GeV) 5 5 3e L MC(GRAPE) 5 L DATA Needs confirmation with independent data M 2 (GeV) 5 5 M 2 (GeV)

104 h ee Excluded via Bhabha Scattering SLAC+PETRA.2 Excluded by OPAL (pair production) Excluded via Bhabha Scattering OPAL Single Production, BR(H ee)=% H Preliminary OPAL Preliminary M H (GeV)

105 (Soft) Physics at HERA II Proton Structure Heavy Quarks Diffraction Jet Physics Electroweak Beyond the SM F % α F 5%... Open charm F 2 -charm J/Ψ B-physics... High t Diffr. jets Vector mesons DVCS... low/high Q 2... NC CC W-production... Leptoquarks Isolated leptons SUSY... Triggering needs for: high Q 2, low Q 2 missing energy/momentum, jets, jet-topologies, tracks, track-topologies, muons, photons, vector mesons, exclusive final states...

106 H Trigger Subsystems FTI [2] Central Tracking System DCRΦ Trigger zvtx Trigger CIP2 Trigger Fast Track Trigger BST Digital Muon System L2TT L2NN L3 [FTT++] ToF Lumi e FPS FNC ToF p Forward Muon System Liquid Argon LAr Trigger Jet Trigger SpaCal

107 The H Trigger System Detector front-end systems 2.3 µs L hardware MHz deadtime free 2 µs L2 neural networks topology analysis khz deadtime: ~2% < µs L3 PPC processor farm 2 Hz deadtime: ~2% ~ ms L4 PC farm 5 Hz deadtime: ~7% Tape < Hz

108 Titel Proton Induced Background Event Run 3396 Event 53 22/4/7

109 Background Rejection with new Central Inner Proportional Chamber COP COZ Optical Readout Modern FPGA Technology Projective Geometry CST Beam CIP CJC z-axis Physics Backgr.

110 Open Charm and the Direct Measurement of the Gluon Density K π + xg(x,q 2 ) Q 2 =2 GeV 2 µ 2 =25 GeV 2 H prel. exp thy D* (DIS) D* (γp) Ereignisse / MeV x M (Kππ s ) - M(Kπ) [GeV] D * electron proton + x g D Golden D * decay electron c c - π s + remnant

111 Fast Track Trigger Concept Group 2 Group 4 CJC 2 Track Group 3 Group CJC Extension of CJC readout system for 4 groups of layers to allow Fast QT analysis 2.3 µs Coarse track finding Precise track reconstr. Momentum reconstruction 25 µs Momentum sums Event reconstruction Invariant mass determ. ~ µs Track based Jet Finding L L2 L3

112 FTT Performance Example Reconstruction of Open Charm via D *+ D o π + K - π + π + s Events Off-line Reconstruction Fast Track Trigger Simulation M = M(Kππ) - M(Kπ) [GeV] Efficiency m(kπ) - m(d ) < 3 MeV m(kπ) - m(d ) < 25 MeV m(kπ) - m(d ) < 2 MeV Estimated Rate [Hz] Efficiency (left hand scale) Rate (right hand scale) Cut on M [GeV]

113 FTT Hardware Realization L QT and Coarse Track Reconstr. Analog drift chamber signals taken directly from existing CJC Hardware QT Analysis done on FPGA Farm with a precision up to about ns Hit Finding Result transferred into shift register for track segment finding/linking L2 Track Reconstruction Tracks are identified as (virtual) clusters in the (/p t - φ) plane L2 Pattern matching using CAMs (content-addressable-memories) left cell boundaries wires hit insertion right L3 Analysis Level track element Commercial processors running appropriate trigger algorithms Use of combinatorial 4- vector calculations L3 adjacent cells

114 FTT L3 Performance Test Time [µs] Search for D* Number of Tracks

115 HERA II Current Status Summer 2 Detector closed; start of machine operation December 2 First ep collisions recorded at HERA II January 22 Close to design specific luminosity... but several problems with e- and with p-ring several month delay L s [cm -2 s - ma -2 ] x x L s =.5 cm -2 s - ma -2 [Design:.8 cm -2 s - ma -2 ] Today: x x First runs with stable luminosity for H and ZEUS However, background conditions still to be improved (vacuum, alignment) x x x [mm]

116 Background conditions H CJC currents 2 and 22 e + I CJC [µa] ep e + only p only p-beam: bkg. ok e-beam: 75 very high e-ind. bkg. conditions not yet reproducible I e (I p ) [ma] Most recent measurement (promising!)

117 Titel H Status Detector ready for data taking... but not yet fully functioning Need more test data CIP needs repair; Jet Trigger & FTT to come

118 Diploma & PhD Topics Ultra-precise F 2 measurement e.g. Berlin Dortmund Prague High statistics jet measurements e.g. Aachen Cracow Munich Diffraction Birmingham Brussels Heidelberg Moscow HQ physics e.g. Birmingham Hamburg Heidelberg Zürich EW physics e.g. Hamburg Liverpool Munich Orsay Searches e.g. Zürich Marseille H [contact: Paul Newman] Amsterdam Argonne London Oxford Cracow London Madrid Bologna Bonn Hamburg Tel Aviv Tokyo Bristol Hamburg McGill Amsterdam London Oxford Columbia Firenze Tokyo ZEUS [contact: Malcom Derrick]