ZEUS TheThe ZEUSZEUS ExperimentExperiment atat HERAHERA

Micro-Vertex Detector The ZEUS Detector and HERA Straw Tube Tracker

The ZEUS Micro-Vertex Detector consists of two parts: The ZEUS Straw Tube Tracker is divided into two modules The ZEUS experiment at DESY at the ep collider HERA has had its first period of data located in the space between the Forward Tracking Detector Õ taking between 1992-2000. Over 100 pb-1 of data were accumulated. Some of the results Barrel part: three double layers of -strip detectors (FTD). It consists of straw tubes. Six sectors are arranged (arranged in 4,10 and 16 ladders which in turn consist of 5 from this period are shown below, labelled as Physics Results Highlights. in a superlayer. Four superlayers constitute each module. modules made out of 2 half-modules (r-z,r-ϕ sensors and They are rotated by four different angles with respect to r-ϕ, r-z sensors) of 512 readout During 2000-2003, both the HERA accelerator and the ZEUS detector were upgraded: channels each) each other to give as much redundancy for the % HERA Upgrade: reconstruction as possible. Õ Forward part: four double layers The luminosity of the HERA machine will be increased by a factor of five through the use (= 4 wheels) of silicon-strip of superconducting focussing magnets close to the interaction region. The goal is to detectors (arranged in 14 -1 sectors which, in turn, consist accumulate 1000 pb of data by 2006. At the same time, spin rotators have been installed Simulated primary of 2 trapezoidal r-ϕ sensors providing longitudinally polarized and beams for the ZEUS and electron which has of 480 readout channels each) experiments. Some of the physics potential of the upgrade program is shown below, started an labelled as Physics Potential of the Upgrade. electromagnetic shower in the % ZEUS Upgrade: endplate of the Central Tracking Carbon fibre structure Õ ZEUS Micro-Vertex Detector (MVD) (left) Barrel module: Ladder: Detector (CTD). Õ ZEUS Straw Tube Tracker (STT) (right) Also shown is the Helix chips This will improve the overall tracking capabilities and increase the acceptance for high- barrel and forward mass and high-Q2 physics. Furthermore, it will allow the reconstruction and tagging of part of the MVD. Connector heavy-flavour particles by tracks displaced from the primary vertex and by secondary vertex reconstruction. Kapton connection Edge of an STT sector with the gas distribution system. Straws are made of Cooling pipe double layers of Kapton foil. A 50µm Cu/Be wire is strung down the middle of each straw.

barrel part forward part Physics Potential of the Upgrade Lower MVD half: e-polarization scheme at HERA Heavy flavours in the

Charged Current DIS Structure Function F2 Charm: 500pb-1 ZEUS 120 ) (pb) 2

100

200 GeV e-p Data 98-99 >

2 e-p SM √s=320 GeV (Q e-p SM (MC) CC TOT

σ 80 -1 √s=320 GeV (50 pb ) Front-end readout electronics, mounted on the detector:

60

e+p Data 94-97

e+p SM √s=300 GeV cc + Õ e p SM (MC) High precision F2 40 e-polarization observed at HERA √s=300 GeV (50 pb-1) Completed MVD during installation: Bottom: 500pb-1 Õ 20 High precision F2 over range in 2 (x,Q ) →αs and xg

0 -1 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1 P 1000pb-1

CC σ ∝ ± ∆α s ≤ 0.003 e ±p (1 P) ∆[]xg = ≈ 3% Larger of the two STT modules: P Polarization xg

Resolution on MW (R ) : 80MeV

After successful installation (forward side): Exclusion limit : MW (R) > 400GeV Õ Sensitivity to bottom contribution to F2

2 2 Neutral Current event, Q ~ 1800 GeV : Hits from a muon track in the tanθ-ϕ Zeus Run 44224 Event 10564 date: 21-01-2003 time: 18:55:07 ZeVis

E=268.23 GeV Et= 88.02 GeV E-p z= 55.09 GeV Ef=227.64 GeV Eb = 40.59 GeV

Er = 0.00 GeV pt= 5.12 GeV px= 1.64 GeV py = 4.85 GeV pz=213.14 GeV plane. One arc-like curve represents t= -0.79 ns t = -1.39 ns t =-100.00 ns t = -0.86 ns The ZEUS Detector phi= 1.24 f b r g The ZEUS Detector the hits in one sector:

XY View ZR View

QCD and Hadronic Final State Neutral and Charged Current Deep Inelastic Scattering ZEUS 0.6 ZEUS • ZEUS 98-00

and Structure Functions (nb) 2 p ZEUS 95-97 10 NLO QCD

(pb/GeV) LO QCD T / d x jet σ d Monte Carlo models /dE 10 -1 < ηjet < 2.5 ZEUS * σ

γ → d < < ZEUS with s s 142 Wγp 293 GeV 0.4 γ* → CC 2 without s s

x=6.32E-5 F 1 (x) x=0.000102 ZEUS NLO QCD fit x = 0.015 x = 0.032 10 x=0.000161 4 x=0.000253 tot. error -1

-log x=0.0004 10 em 2 x=0.0005 5 F x=0.000632 2 x=0.0008 -2 ZEUS 96/97 0.2 10 x=0.0013 BCDMS 0 E665 -3 x=0.0021 10 NMC jet energy scale uncertainty 4 0.5 NLO uncertainty x=0.0032 x = 0.068 x = 0.13 0 0 x=0.005 2 0.5 0.6 0.7 0.8 0.9 1 1.1 x -0.5 p (data-NLO)/NLO x=0.008 -1 3 1 First evidence for strange sea using 20 30 40 50 60 70 80 90 E jet (GeV) x=0.013 leading ϕ(1020) mesons (above) T x=0.021 0 Impressive range in jet ET covered x=0.032 1.5 by the ZEUS experiment (above) 2 The strong coupling constant αs is x=0.05 x = 0.24 x = 0.42 expected to run with the scale Q -> good agreement with NLO pQCD 1 x=0.08 (below right): ZEUS x=0.13 ZEUS 98-00 Physics Results Highlights Õ Jet cross-sections measured in

0.5 s x=0.18 0.25 -1 1 CCFR α γ ZEUS (82 pb ) (inclusive jet p) α ZEUS (38 pb-1) (dijet DIS) x=0.25 ZEUS-S neutral current DIS to extract s -1 0 ZEUS (39 pb ) (inclusive jet DIS) x=0.4 Exotics Searches - Limits on Flavour Heavy Flavours – Charm Production Õ Data are consistent with each ∆(xF3,FL) Exotics Searches - Limits on Flavour Heavy Flavours – Charm Production 0.2 Bethke 2002 x=0.65 Changing Neutral Current Interactions ZEUS other and with the world average 2 3 4 2 3 4 Changing Neutral Current Interactions –

cc 0.6

0 2 2 3 4 5 1 10 10 10 10 1 10 10 10 10 2 2 Õ Errors are competitive with those

F 4 7 1 10 10 10 10 10 2 2 The production of Q = 2 GeV Q (GeV ) ZEUS (prel.) 0.15 2 2 98-00 of the world average Q (GeV ) charm in DIS is a 0.4 ZEUS 96-97 ZEUS NLO Õ ZEUS is producing some of the The structure function for Charged Single top can be direct probe of the QCD The proton structure function F has CC most precise QCD measurements 0.1 2 Current (CC) interactions F2 has produced at HERA gluon density in the 0.2 in the world 2 been measured in Neutral Current been measured (above), extending a through flavour 10 10 ± proton. µ (GeV) (NC) e p scattering and exhibits clear fixed target measurement to higher changing neutral 0 11 18 30 4π scaling violations (above). These momentum transfer current anomalous α (Q ) = + ... Running within one experiment is consistent s 2 2 with the renormalisation group equation scaling violations have been used to coupling, mediated 0.4 β 0 ln( Q / Λ ) ZEUS determine the strong coupling by a (k γ) or ) tu constant, α , and the parton densities 2 0 0.2 s a Z (vtuZ) Diffraction - Deep Inelastic Virtual Compton Scattering (below) 10 ZEUS (prel.) e+p NC 99-00 (pb/GeV

2 − 0 ZEUS e p NC 98-99 60 1 + 130 500 * /dQ SM e p NC (CTEQ6D) Perturbative QCD models: γ  γ

σ Elastic scattering: p p ZEUS − 0.8 d -1 SM e p NC (CTEQ6D) ZEUS

xf 10 0.4 2 2 Probing two partons with ZEUS NLO QCD fit Q =10 GeV κ e’ tuZ γ-v exclusion region α 2 -2 tu tuZ (M ) = 0.118 v 0.7 s Z 10 No excess with different longitudinal momenta 1 0.2 e xu ZEUS (prel.) 94-00 γ tot. error v -3 respect to (x ≠ x ) γ 0.6 10 The measured structure 1 2 * Mtop=170 GeV CTEQ 6M Mtop=175 GeV function for charm 0 2 -4 0.8 -5 -3 -5 -3 -5 -3 Q 10 predictions has Mtop=180 GeV 10 10 10 10 10 10 ZEUS 0.5 MRST2001 + cc x 8 + ZEUS e p CC 99-00 production, F2 (above ZEUS 96-00 e p (95.0 pb-1) − been observed. − -5 ZEUS e p CC 98-99 ZEUS 98-99 e p (16.7 pb-1) 10 + right) is in good agreement with the NLO QCD prediction x1 x2 × SM e p CC (CTEQ6D) 7 δ + 0.4 xg( 0.05) − 0.6 Excluded by CDF W fit to e p data -6 SM e p CC (CTEQ6D) 95% confidence p) (nb) xd based on the gluon density extracted from a fit to inclusive γ v 10 limits have been 6 0.3 ZEUS DIS data → -7 p κ γ=v =0 p 2 2 p’ 10 evaluated. 0.4 tc tcZ * Q = 9.6 GeV

3 4 γ

10 10 ( 5

0.2 σ xS(× 0.05) 2 2 Charm production in DIS has Q (GeV ) HERA Excluded by L3 been measured from the rate 4 ± experiments are 0.2 The steep rise as a function of 0.1 Neutral and Charged e p deep of D*± mesons. The most sensitive to 3 2  inelastic scattering cross sections fragmentation functions of W ( 1/x) can be explained 0 have been measured (above). At the γ exchange. 0 by parton density in the proton -3 -2 -1 0 0.2 0.4 0.6 0.8 1 charm into different charmed 2 κ + +0.08 10 10 10 1 highest momentum transfer, the NC γ e p: δ=0.75 ± 0.15(stat.) (syst.) x tu at HERA were found −0.06 and CC cross sections are of to be in agreement with LEP 1 DVCS is a hard process comparable magnitude. This is a For low values of the vtuZ coupling, ZEUS improves data. The two plots (right) 0 graphical verification of electroweak on the limits set by LEP and the Tevatron. show the fraction of strange 40 60 80 100 120 140 unification. W (GeV) ( s) and vector (Pv) mesons.

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