status of the zeus collaboration" study of heavy quark production at hera using the zeus microvertex...

Nikhef Jaarvergadering (21-22/12, 2004)Radboud Universiteit

Nikhef Jaarvergadering (21Nikhef Jaarvergadering (21--22/12, 2004)22/12, 2004)Radboud UniversiteitRadboud Universiteit

Status of the ZEUS CollaborationStatus of the ZEUS CollaborationMMóónica nica L. VL. Váázquezzquez AcostaAcosta

e+

p

Status of the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) NIKHEF Jaarvergadering, 21-22/12, 2004 - 2

HERA: ep ColliderHERA: ep ColliderHERA: ep Collider

H1: ep interactions

HERA-B: p beam+fixed target

HERMES: polarised e + fixed target

ZEUS: ep interactions

920 GeV protons27.5 GeV positrons


ZEUS-NIKHEF Group StructureZEUSZEUS--NIKHEF Group StructureNIKHEF Group Structure

Seniors: Paul KooijmanEls Koffeman Tracking CoordinatorHenk TieckeLeo Wiggers

PostDocs:Nicola Coppola Run CoordinatorMónica Vázquez Radiation Monitor Coordinator

Students:Gabriel Grigorescu Calorimeter DQMAvraam Keramidas Calorimeter DQM


ZEUS-NIKHEF thesis defences in 2004ZEUSZEUS--NIKHEF thesis defences in 2004NIKHEF thesis defences in 2004

Sven Schagen (Jan. 2004)" Charm in the proton : an analysis of charm production in

deep inelastic scattering "

Sjors Grijpink (Apr. 2004)" Charged current cross section measurement at HERA "

Erik Maddox (Dec. 2004)" Study of heavy quark production at HERA using the

ZEUS microvertex detector "


Background problems in HERA-II solved!Background problems in HERABackground problems in HERA--II solved!II solved!

Measures taken:• Additional collimators far upstream of IPs• Change in masking at ZEUS (critical)• Additional pump near IP at H1• Increased conductance of pumping ports• Warm up of sc magnets during scheduled maintenance• Steady operations with high beam currents

HERA-II no longer current-limited due to backgrounds

Shutdown 2003

mea

sure

of b

ackg

roun

d

positron beam current


Peak luminosity 1.2 pb-1d-1

Best week 0.9 pb-1d-1

2004 Average 0.4 pb-1d-1

~50 days of operations lost

Due to major technical failures

Operational efficiency needs to be improved

HE RA Opera tion a l S ta tis tics 2 004

Fault34%

p-Inj9%

Lum in.R un35%

Machine Studie s

11%

Ex pe rim e nt0%

Shutdow n3%

e -Inj7%

Lum ituning1%

∫2004Ldt = 87pb-1∫2004Ldt = 87pb-1

2004 Luminosity accumulation2004 Luminosity accumulation2004 Luminosity accumulation

Problems due to large coasting beam caused byRF problem and after a vacuum leak NR

running day

Lum

inos

ity [p

b-1 ]


ZEUS gated Luminosity ZEUS gated Luminosity ZEUS gated Luminosity

Efficiency loss due to: • Bad conditions in the initial tuning after luminosity is declared,

which prevents to switch on the tracking chambers• DAQ problems which now have been solved

Most of the ZEUS data is good MicroVertexDetector(MVD) data

ZEUS gated: 43.7 pb-1


The MVD is there ...The MVD is there ...The MVD is there ...

• All vertices in the XY plane with -25 cm < Z < 25 cm• The interactions in the material of the beampipe and the MVD are clearly seen

Ladders 3% Xo


MVD Alignment with cosmic muonsMVD Alignment with cosmic muonsMVD Alignment with cosmic muons

うQ’

Q

P

P

MVD alignmentminimize the difference betweenthe expected track position andthe measured hit position

cosmic track reconstruct as 2 tracks

( )0ZσThe mismatch distribution has a width of 97 µm after alignment

Before alignment

After alignment


Impact parameter resolution from the MCErik Maddox

Impact parameter resolution from the MCImpact parameter resolution from the MCErik MaddoxErik Maddox

Impact parameter: point of closest approach of the track to the coordinate where the track is generated

Useful quantity to tag beauty events

tracks with 140 < φ < 210 degrees are measured only with two outer cylinders:resolution significantly worse


Impact parameter resolution from the dataImpact parameter resolution from the dataImpact parameter resolution from the data

cosmic track reconstruct as 2 tracks

( )0Zσ

After MVD alignment

Difference of two independent tracks so divide by √2 : 83/pt + 47 µmMC resolution impact parameter resolution : 56/pt + 18 µm (perfect geometry)

This satisfies the design criterium of an impact parameter resolution of 100 µm


Radiation damage in the MVDRadiation damage in the MVDRadiation damage in the MVD

• No evidence of significant radiation damage- Mean signal size stable- Uncontrolled proton beam loss (4 Nov 03) caused 10% drop in signal

- Big effort of HERA to reduce the risk to


D+: charm tagging with the MVDErik Maddox

DD++: charm: charm taggingtagging with the MVDwith the MVDErik MaddoxErik Maddox

The combinatorial background is reduced by a factor 45 and the signal by a factor 2.7

Submitted to ICHEP2004


Event display of a DIS D+ candidateEvent display of a DIS DEvent display of a DIS D++ candidatecandidate

Q2 = 160 GeV2pt(D+)=5.1 GeV


D*: charm tagging in DIS (Q2 >1 GeV2)Gabriel Grigorescu

DD**: charm: charm taggingtagging in DIS (Qin DIS (Q22 >1 GeV>1 GeV22))Gabriel GrigorescuGabriel Grigorescu

SS0* kDD ππ→π→

GeV5.1)D(p *t >

GeV5.2)D(p *t >

148.0)DD(M142.0 0*


Beauty tagging: semi-leptonic decays to muons in dijet events

Beauty tagging: Beauty tagging: semisemi--leptonic decays to muons in dijet eventsleptonic decays to muons in dijet events

Beauty mass larger: distribution of the transverse momentum of the muon wrt the jet axis is expected to be harder


Beauty tagging using the MVD:Muon impact parameter reconstruction

Beauty tagging using the MVD:Beauty tagging using the MVD:Muon impact parameter reconstructionMuon impact parameter reconstruction

Impact parameter:distance of closest approach of the muon with respect to the primary vertex

Expected beam width:σX ≈ 112 µm, σY ≈32 µm

Measured vertex resolution:σX≈ 100 µm, σY ≈140 µm

• Difference of the positive and negative δ• Compatible with beauty+charm prediction andthe beauty fraction obtained with the ptrel fit

Combined ptrel , δ fit on the way ...


HERA-II: lepton beam longitudinal polarizationHERAHERA--II: lepton beam longitudinal polarizationII: lepton beam longitudinal polarization

e-L e+RP= -1 P= 1uL

Rd

dL

Ru

Polarization in collisions: 30-40%

Polarization without collisions up to 50%

Faster polarization measurements neededfor better optimization

W only couples to left-handed fermions and right-handed antifermions


PentaQuark Searches in ZEUSPentaQuark Searches in ZEUSPentaQuark Searches in ZEUS

MeV)syst()stat(5.15.1521:M 8.2 7.1+−±

?!pK0S

−Θ≡

4.6 σ

BW Fit: Γ= 8 ± 4 MeV

N(1710)

Σ(1890)

pK0S→Θ+


The NA49 signal (Ξ − −) search in ZEUSThe NA49 signal (The NA49 signal (Ξ Ξ −− −−) ) search in ZEUSsearch in ZEUS

→pπ-→Λ0π-

Ξ--→ Ξ-π-

Clean but ...No pentaquark signal

)1530(0 2/3Ξ


5.4 σ

The charmed pentaquark search The charmed pentaquark search The charmed pentaquark search

22 GeV1Q >

ZEUS sees no signal for DIS or photoproduction

Upper limit at 95% CL

R< 0.23 %R< 0.35% for Q2 > 1 GeV2R


Searching for:Θc -> D* p Θ+ -> KS p

in DIS eventsQ2 > 20 GeV20.03 < y < 0.740 < E-pz < 65 GeV

Pentaquark searches in HERA-II dataAvraam Keramidas

Pentaquark searches in HERAPentaquark searches in HERA--II dataII dataAvraam KeramidasAvraam Keramidas

Proton identification

MVD dE/dx

dE/d

x (m

ips)

p (GeV)

dE/dx determination1) Path length normalisation: PHnew = PH*cos(1) Path length normalisation: PHnew = PH*cos(ΨΨ). ).

2) Truncated mean: To reduce effect of the landau tail, 2) Truncated mean: To reduce effect of the landau tail, the biggest PHnew is discarded. the biggest PHnew is discarded.

3) Final averaging: The remaining PHnews are simply averaged.3) Final averaging: The remaining PHnews are simply averaged.

p

k

π


Pentaquark searches in HERA-II dataAvraam Keramidas

Pentaquark searches in HERAPentaquark searches in HERA--II dataII dataAvraam KeramidasAvraam Keramidas

D*

Ks

pD*C →Θ

pKs→Θ+

M(KSp) [GeV]

M(D*p) [GeV]


Present statusPresent statusPresent status

Currently in the startup phase of electron runningHERA has not run with electron beams since 1999 (L=17 pb-1)

[ ]L2232242

2

2

Fy - )Q(x,xFY)Q(x,FY xQ2 X)e pe(dQdx

σd−+

πα=±→± m

xF3 is obtained from the difference of σ(e-p) − σ(e+p)Precision currently limited by low e- statistics


First e- event (photoproduction candidate)06/12/2004 02:26am

First eFirst e-- event (photoproduction candidate)event (photoproduction candidate)06/12/2004 02:26am06/12/2004 02:26am


ProspectsProspectsProspects

2005 HERA runs with electrons

2006 HERA runs with positrons

2007 6-month extension of HERA run

NIKHEF contribution to ZEUS has been reduced by 50%

for 2005 and 2006

After 2006 the NIKHEF ZEUS programme is officially ended

HERA: ep ColliderZEUS-NIKHEF Group StructureZEUS-NIKHEF thesis defences in 20042004 Luminosity accumulationZEUS gated LuminosityThe MVD is there ...MVD Alignment with cosmic muonsImpact parameter resolution from the MC Erik MaddoxImpact parameter resolution from the dataRadiation damage in the MVDEvent display of a DIS D+ candidateD*: charm tagging in DIS (Q2 >1 GeV2) Gabriel GrigorescuBeauty tagging: semi-leptonic decays to muons in dijet eventsBeauty tagging using the MVD:Muon impact parameter reconstructionHERA-II: lepton beam longitudinal polarizationPentaQuark Searches in ZEUSThe NA49 signal (X - -) search in ZEUSPentaquark searches in HERA-II data Avraam KeramidasPresent statusFirst e- event (photoproduction candidate)06/12/2004 02:26amProspects

status of the zeus collaboration" study of heavy quark production at hera using the zeus microvertex...

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