ZEUS Status Report Recent Results and Progress PRC, DESY

Size: px

Start display at page:

Download "ZEUS Status Report Recent Results and Progress PRC, DESY"

Rosamund Garrett
5 years ago
Views:

1 7 th May 4 Recent Results and Progress PRC, DESY Richard Hall-Wilton (University College London) ZeVis Zeus Run 4883 Event 969 date: 8--4 time: 9:5:54 E=6 GeV E t=9 GeV E r = GeV p t=.6 GeV phi=.66 t =-.8 ns f E e =73. GeV =.84 e Q =6757 GeV e,da E-p z=53. GeV p x=.7 GeV t =-.4 ns b E f=7. GeV p y=.6 GeV t =.66 ns r E b =34 GeV p z =8 GeV t g =3.5 ns θ φ =.64 e x =. y =.56 e,da e,da Running Conditions Detector Status Results from Recent Data Q = 6677 GeV XY View ZR View Physics Highlights Summary

2 Background levels At the last PRC the extrapolated backgrounds at high beam currents above the safe operating level for the CTD Pumping procedure and cleaning with beam has cleared up the proton background problems Even at maximum anticipated beam currents, below the CTD safe operating level Proton Background problems solved! 7 th May 4 Richard Hall-Wilton, UCL

3 Luminosity since the last PRC HERA delivered 5 pb taken pb A closer look at the efficiency Integrated Luminosity (pb - ) HERA delivered gated running day 7 th May 4 3 Richard Hall-Wilton, UCL

4 Luminosity Delivered per Week luminosity (nb - ) efficiency started at 4% Presently 5-6% CTD HV required to be on for data taking ep runs o.k. ep runs week luminosity (nb - ) /HERA HERA delivered gated week Spiky Background week delivered gated physics/all gated Nearly all data taken can be used for physics week 7 th May 4 4 Richard Hall-Wilton, UCL

Deadtime (5% CTD CURRENT HERA DELIVERED LUMINOSITY GATED LUMINOSITY beginning of fill, 5% later)

5 Efficiency Examples of good and bad fills Fills from Last Week Bad Fill Efficiency - 47% Regular trips Half way through the fill CTD became inoperable Good Fill Efficiency - 68% Occasional Trips DAQ Deadtime (5% CTD CURRENT HERA DELIVERED LUMINOSITY GATED LUMINOSITY beginning of fill, 5% later) Occasional DAQ glitches Loss before detector is on More typical since last weekend 7 th May 4 5 Richard Hall-Wilton, UCL

6 Efficiency Improvements Beam conditions become very spiky as the fill ages Working closely with HERA to solve this CTD trip thresholds have been increased to reduce sensitivity Provided information on the spikes to HERA Large effort from HERA Conditions are improving DAQ Deadtime Caused by huge size of events in DAQ system due to background Solution: Use new Global Tracking Trigger at SLT to reject these events Fully implemented by the end of this week DAQ Glitches Problems identified Efficiency is improving Improving luminosity procedure 7 th May 4 6 Richard Hall-Wilton, UCL

7 Luminosity Monitor Upgrade 6m Tagger Status E / E Necessary to achieve % precision γ-cal energy calibration Spectrometer acceptance calibration Rebuilt and installed in November Data in coincidence with Spectrometer: Energy sum within % Final integration with γ calorimeter trigger ongoing.6.4. E E = 6.5% E 5% beam energy / GeV energy sum for tag6 energy > 4 GeV sum_histx Entries 6487 Mean 6.74 RMS.6 Constant 55 ± 3. Mean 7.7 ±. Sigma.8 ± spec + tag6 energy/gev 7 th May 4 7 Richard Hall-Wilton, UCL

8 Micro Vertex Detector No evidence of significant radiation damage during routine HERA operation Mean signal size stable (S/N ) Uncontrolled Proton beam loss (4 Nov) caused % drop in signal Enormous effort from HERA to reduce this risk (exp. < to end of HERA) Noise shows shallow slope Corresponds to 6 krad in 5 days on innermost cylinder 5 krad expected by end of HERA II Front End Chips tested to 3 krad Do not expect major damage from radiation Detector in good shape Bad channels stable < % First physics results using MVD... 7 th May 4 8 Richard Hall-Wilton, UCL

9 Straw Tube Tracker After major work on STT during last summers shutdown: STT stable and included in luminosity running STT running at full voltage since December 3/48 sectors have low efficiency (though stable) Not a problem for track finding as there is redundancy Being implemented into SLT (GTT) Work ongoing to tune the tracking Number of hits indicate high efficiency of pattern recognition 4 7 th May 4 9 Richard Hall-Wilton, UCL

10 Recent Data STT Tracking ZeVis Zeus Run Event 397 date: 8--4 time: :5:3 E=8.73 GeV E r= GeV phi=.74 E t=.58 GeV p =.55 GeV t t f= ns E-p z=.558 GeV p x=-.34 GeV t b= ns E f=8.7 GeV p y=. GeV t r= ns E b p z t g =.654 GeV =8.7 GeV = ns ZR View ZR View Selecting low multiplicity events from Data to tune the Monte Carlo STT matching with CTD and MVD found tracks ongoing 7 th May 4 Richard Hall-Wilton, UCL

11 Recent Data Neutral Current Events Events Q DA (GeV ) 3 θ e (rad) Events Events x DA Q > GeV NC (prel.) 3-4 (6.7 pb - ) NC MC (DJANGOH) 3 γ h (rad) Neutral Current, Q > GeV 5 events for 6.7 pb Preliminary result for Moriond EW Monte Carlo describes Data well Understand and model the observed hadronic and electon final states Also confirms the luminosity measurement Events 3 Events P T, h (GeV) -4-4 Z VTX (cm) 7 th May 4 Richard Hall-Wilton, UCL

12 Recent Data J/ψ and D Production Combinations J/ψ Candidates D* + K - π + π + + (c.c) Luminosity = pb ± P T (D* ) > 3. GeV ± N(D* ) = 4 ± 3-4 Data 58 - Candidates Data 5 pb M (GeV) 4 D Candidates M(µµ) GeV CTD performance is good Tracking using MVD + CTD Tracking working well 7 th May 4 Richard Hall-Wilton, UCL

13 Recent Data D + Signal Use the MVD to tag secondary vertices from charm: P D + S K π + π + Combinations 5 Combinations (prel.) 3-4 (5pb ) D + K - π + π + + (c.c.) 5 - (prel.) 3-4 (5pb ) Fit ± N(D ) = 86 ± > 5. σ L L 4 D + K - π + π + + (c.c.) M(Kππ) (GeV) M(Kππ) (GeV) Can define a significance of seperation of secondary and primary vertices: L = S P No signal visible before Signal enhanced by cutting on significance parameter Encouraging! 7 th May 4 3 Richard Hall-Wilton, UCL

14 Recent Data Charged Current ZeVis Zeus Run 484 Event 4 date: 6--4 time: :58:8 E=88.5 GeV E t=48. GeV E-p z=5. GeV E f=35.4 GeV E b =53. GeV E r = GeV p t=44.7 GeV p x=4.6 GeV p y=-37.3 GeV p z =63.4 GeV phi=-.99 t =5.9 ns t =-8.5 ns t =6.4 ns t =.9 ns f b r g E =.4 GeV θ =. φ =-.3 x =.9 y =.47 Q e e,da =455 GeV e e e,da e,da XY View ZR View Q = 3433 GeV, /P T = 45 GeV 7 th May 4 4 Richard Hall-Wilton, UCL

15 Polarised Charged Current Cross Section Charged Current cross section from October 3 - March 4 Data Right-handed e + polarisation Average +33% polarisation Preliminary result for Moriond EW Cross Section for Q > 4 GeV : σ cc = 38. ±. (stat.) ±.8 (sys.) ±. (lumi.) ±.8 (pol.) pb Cross section above unpolarised value In agreement with standard model σ CC (Q > 4 GeV ) (pb) σ CC /σ CC SM(P=) (prel.) e + p 3-4 (6.6 pb - ) e + p 99- (P=) SM (CTEQ6D) P Spin direction was changed April 7 th May 4 5 Richard Hall-Wilton, UCL

16 Recent Physics Output new papers since last PRC DIS4: 5 new preliminary results 55 abstracts submitted to ICHEP 4 abstracts on HERA II data. Instantons. Beauty photoproduction at HERA 3. High Q Neutral Current Cross Sections in e+p DIS at root(s)=38 GeV 4. Search for Contact Interactions, large extra dimensions, finite quark radius 5. Photoproduction of D* Mesons associated with a Leading Neutron Have a look at some of the highlights from recent results now Observation of Isolated High ET Photons in DIS 7. Pion Trajectory 8. Exclusive Electroproduction of J/Psi Mesons at HERA 9. The dependence of dijet production on photon virtuality at HERA. Evidence for a narrow baryonic state decaying to Ks (anti)proton. Beauty in DIS. Substructure dependence of jet cross sections and determination of alphas 7 th May 4 6 Richard Hall-Wilton, UCL

17 Combinations /.5 GeV KS p(p) Q > GeV χ / ndf =35 / 44 events= ± peak= 5.5 ±.5 MeV width= 6. ±.6 MeV Strange Pentaquarks 96- Fit Gaussian Background ARIADNE MC M (GeV) K K S S p p Accepted by Phys. Lett. B Select p K s combinations Peak at 5.5 ± MeV Width above but compatible with experimental resolution Signal present in both charge combinations Interpreted as Θ ± pentaquark Significance 4.6σ Pentaquark spectroscopy and searches become an active area of physics at HERA 7 th May 4 7 Richard Hall-Wilton, UCL

18 Pentaquark searches Entries / 7.5MeV Ξ (53) (prel.) 96- Fit Q > GeV NA49 report resonance in Ξ π at.86 GeV Signal / Ξ (53) candidates=6±34 peak=533.5±.4 MeV σ=7.6±.4 MeV anticipated NA49 signal M(Ξπ)(GeV) sees no evidence of a signal Clearer Ξ (53) signal Larger statistics and smaller background 7 th May 4 8 Richard Hall-Wilton, UCL

19 Combinations /.5 MeV (prel.) 995- (6.5 pb - ) backgr. wrong charge N(D* ± ) = 473 ± M(Kππ s ) - M(Kπ) (GeV) Charm Pentaquark Search H has reported resonance at 3. GeV in M(D p) Interpreted as charmed pentaquark Search by shows no evidence for signal at 3. GeV Inclusive D sample 43 DIS D sample 97 Combinations / MeV 8 6 (prel.) 995- (6.5 pb - ) P(p) <.35 GeV, dedx(p) > max(.3,.3/p(p) +.8) fit: A ( M ext -m p ) B exp[-( M ext -m p )C] fake signal of.3% from N(D ± ) Combinations / MeV 4 8 (prel.) 995- (6.5 pb - ) P(p) > GeV, dedx(p) < /P(p) +. fit: A ( M ext -m p ) B exp[-( M ext -m p )C] fake signal of.4% from N(D ± ) Gaussian shows expected signal for N(Θ c )/N(D ) = % M(D p) = M ext + M(D + ) PDG (GeV) M(D p) = M ext + M(D + ) PDG (GeV) 7 th May 4 9 Richard Hall-Wilton, UCL

20 Beauty Production at HERA Papers published on beauty production in DIS and PhP PhP: subm to Phys. Rev. D DIS: subm to Phys. Lett. B PhP result: Good agreement with NLO dσ/dp T b (pb/gev) b µ b e NLO QCD dσ/dp b T (ep ebx) Q <GeV η b <.<y<.8 Data / Theory b Cross Sections at HERA σ vis (jjµx) p rel T -.6 < η µ < -.9, p µ >.5 GeV σ vis (jjµx) p rel T -.9 < η µ <.3, p µ T >.5 GeV σ vis (jjµx) p rel T.48 < η µ <.3, p µ > 4 GeV, p µ T > GeV H σ vis (jjµx) Imp.-Par. p rel T (prel.) H σ vis (ejµx) Imp.-Par. p rel T (prel.) σ vis (ejµx) p rel T DIS result - st publication on this topic HERA I message on beauty production: p T b (GeV) 3 NLO QCD Good agreement between data and NLO pqcd Q [GeV ] 7 th May 4 Richard Hall-Wilton, UCL

21 Exclusive J/ψ Production in DIS All of HERA I Data published (paper subm. to Nucl. Phys. B) Precision of the data impressive J/ψ pqcd should be applicable Cross Section sensitive to gluons σ (gluon) Data distinguishes between PDF fits Clear sensitivity to the gluon Need NLO to be able to constrain the gluon with the data σ(γ * p J/ψp) (nb) σ(γ * p J/ψp) (nb) - - (a) // (b) // Photoproduction DIS 98- MRT (-S).49 MRT (CTEQ6M). MRT (MRST).98 δ Q (GeV ). ( ).4 (.) 3. (.) 6.8 (.5) 6. (.3) W (GeV) < W > = 9 GeV - Q (GeV ) σ W δ 5 5 Q (GeV ) 7 th May 4 Richard Hall-Wilton, UCL

22 Charged and Neutral Current DIS Cross Section Measurements Charged and Neutral Current dσ/dq (pb/gev ) e + p NC 99- e p NC SM e + p NC (CTEQ6D) SM e p NC (CTEQ6D) Cross sections for e + p and e p published Above Q GeV Electroweak Unification Standard model - excellent description of the data e + p CC 99- e p CC SM e + p CC (CTEQ6D) SM e p CC (CTEQ6D) Complete picture from HERA I Use this data in QCD fits Q (GeV ) 7 th May 4 Richard Hall-Wilton, UCL

23 New QCD Fits Add high Q data into - Only structure function fit Full HERA I data set All 94- e ± p Data Compare to published -S Include Fixed target data Data Good agreement -Only Fit still needs additional constraint for x>. HERA II Data at high x Use jets data in the fit 7 th May 4 3 Richard Hall-Wilton, UCL

24 Very precise jet data from Adding Jet Data to QCD Fits Include jet data in QCD fits Rigorous Inclusive DIS jet data High E T dijet PhP Data (x γ >.75) Compare -Only fit with + without jet data Jet data constrain gluon at medium x Improved precision at high x xg O Q = GeV -O (prel.) 94- uncorrelated error correlated error Q = GeV Q = GeV -JETS Q = GeV -JETS (prel.) Q = GeV Q = GeV th May 4 4 Richard Hall-Wilton, UCL x

25 Adding Jet Data to QCD Fits DIS Jet data used in the QCD fit Fit describes the data well Note precision of cross sections Jet energy scale uncertainty % (pb/gev) B T,jet dσ/de (DIS data) Jet Energy Scale Uncertainty NLO QCD δ had δ Z : -JETS (prel.) 94- total uncertainty 5 < Q 5 < Q 5 < Q < 5 GeV 5 ( ) < 5 GeV 4 ( ) < GeV 3 ( ) < Q < GeV ( ) < Q < 5 GeV ( ) - Q > 5 GeV ( ) B E T,jet (GeV) 7 th May 4 5 Richard Hall-Wilton, UCL

26 Jet Substructure QCD predicts: gluon initiated jets broader than quark initiated jets (narrow) The scattering angle θ sensitive to spin of exchanged particle Use dijet events to investigate the underlying parton dynamics dσ/dcosθ broad jet, narrow jet for events with broad Dominant diagrams cosθ ± different Positive-negative assymetry + t-channel gluon exchange - u-channel quark exchange QCD subprocesses separated for first time (arbitrary units) * dσ/cos θ broad q g 98- γp (broad-narrow jets) q g q PYTHIA jet shape selection q g g q g subm. to Nucl. Phys. B * cos θ broad 7 th May 4 6 Richard Hall-Wilton, UCL

27 α s Measurements from Large number of α s measurements from Compatible with world average World average does not include measurements Individual measurements competitive with world average th. uncert. exp. uncert. Inclusive jet cross sections in γp (Phys Lett B 56 (3) 7) Subjet multiplicity in CC DIS (Eur Phys Jour C 3 (3) 49) Subjet multiplicity in NC DIS (Phys Lett B 558 (3) 4) Jet shapes in NC DIS (DESY hep-ex/4565) NLO QCD fit (Phys Rev D 67 (3) 7) Inclusive jet cross sections in NC DIS (Phys Lett B 547 () 64) Dijet cross sections in NC DIS (Phys Lett B 57 () 7) World average (S. Bethke, hep-ex/)...4 α s (M Z ) 7 th May 4 7 Richard Hall-Wilton, UCL

28 Outlook Vast improvement in beam conditions and luminosity Enormous efforts by HERA Very good cooperation between HERA and all experiments Thanks to HERA as well as H and HERMES Detector in good shape, efficiency improving Wealth of results from HERA I data and... First results from HERA II coming in. Looking forward to running with electrons later this year!! XY Q GeV View ZR View 7 th May 4 8 Richard Hall-Wilton, UCL

Richard Hall-Wilton University College London. July 2002

PPRP, Richard Hall-Wilton University College London July 2002 July 2002, RAL Overview Introduction to HERA and ZEUS Detector Status Central Tracking Detector Microvertex Detector Global Tracking Trigger