Current Projects in the ZEUS collaboration

MMóónicanica L. VL. Váázquez Acostazquez Acosta

Max Planck Institute, Munich, 09.05.2005

Current Projects in the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) MaxMax--Planck Intitute MunichPlanck Intitute Munich, 09/05, 2005 - 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

Current Projects in the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) MaxMax--Planck Intitute MunichPlanck Intitute Munich, 09/05, 2005 - 3

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

HERA-II no longer current-limited due to backgrounds

mea

sure

of b

ackg

roun

d

positron beam current2001: Luminosity upgrade & new silicon detector (MVD)2002-2003: background struggle

Measures taken:• Additional collimators far upstream of IPs• Additional pump near IP Shutdown 2003

Current Projects in the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) MaxMax--Planck Intitute MunichPlanck Intitute Munich, 09/05, 2005 - 4

ZEUS Gated Luminosity ZEUS Gated Luminosity ZEUS Gated Luminosity

ZEUS gated: 43.7 pb-1

ZEUS gated: 48.36 pb-1

plot 09/03/05

Most ZEUS data is good MicroVertexDetector(MVD) data

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

Current Projects in the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) MaxMax--Planck Intitute MunichPlanck Intitute Munich, 09/05, 2005 - 5

Radiation Monitor SystemRadiation Monitor SystemRadiation Monitor System

zx-Querschnitt

4x2 PIN diodes 4x2 PIN diodes

-100 cm

110 cm

BMVDFMVD

z=160 cm -120 cm-130 cm

4 RadFET

X

Z

4 RadFET8 RadFET

8 RadFET

Silicon PIN diodesInstantaneous dose rate from signal currentAutomatic dump systemBulk damage from offset leakage-current

Radiation Field Effect Transistors (RadFETs)Monitor surface damage from shift in threshold voltage

Current Projects in the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) MaxMax--Planck Intitute MunichPlanck Intitute Munich, 09/05, 2005 - 6

Silicon pin diodes: fast radiation monitorSilicon pin diodes: fast radiation monitorSilicon pin diodes: fast radiation monitor

Threshold alarm: 1000 nA ~ 0.02 kRadThreshold dump: 4000 nA ~ 0.08 kRrad Forgiveness rate: 10 nA/s : allows short-term increase during injection and

small constant background

• 25 kRad expected dose in the MVD by end of HERAII• Front end chips tested up to 300 kRads

Maximumfill level

ffill ∝Isignal = Idiode - Ileakage

fforgiveness

Actualfill level

bucket overflow→ beam dump

Dump signal to HERA

Current Projects in the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) MaxMax--Planck Intitute MunichPlanck Intitute Munich, 09/05, 2005 - 7

Silicon Pin Diodes: leakage currentsSilicon Pin Diodes: leakage currentsSilicon Pin Diodes: leakage currents

Diodes on ring inside,closest to beamline

ShutdownProton beam-loss accident

Long term increase and annealing of leackage currentSubtract pedestal before each fill

Current Projects in the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) MaxMax--Planck Intitute MunichPlanck Intitute Munich, 09/05, 2005 - 8

RADFETs: integrated doseRADFETs: integrated doseRADFETs: integrated doseD

ose

(kR

ad)

MVD (-0.6m) REAR (-1.7m)C5 (-1m) FORWARD (1.3m)

Steady increase during beam operationStep like increase from single beam-loss accidentsValues expected higher in rear than in MVD (-0.3m) due to:• backscatter in C5 collimator• synchrotron radiation and off momentum positrons

Current Projects in the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) MaxMax--Planck Intitute MunichPlanck Intitute Munich, 09/05, 2005 - 9

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 <1 till end of running

- Noise shows a shallow slope- Corresponds to 6 kRad in 500 dayson innermost cylinder

• Detector in good shape- Bad channels stable <2%

Current Projects in the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) MaxMax--Planck Intitute MunichPlanck Intitute Munich, 09/05, 2005 - 10

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

Current Projects in the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) MaxMax--Planck Intitute MunichPlanck Intitute Munich, 09/05, 2005 - 11

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

Current Projects in the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) MaxMax--Planck Intitute MunichPlanck Intitute Munich, 09/05, 2005 - 12

Impact parameter resolution from cosmicsImpact parameter resolution from cosmicsImpact parameter resolution from cosmics

cosmic track reconstruct as 2 tracks

( )0Zσ

After MVD alignment

Difference of two independent tracks so divide by √2 : 83/pt + 47 µm

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

Current Projects in the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) MaxMax--Planck Intitute MunichPlanck Intitute Munich, 09/05, 2005 - 13

Tracking quantities in ep DIS dataTracking quantities in ep DIS dataTracking quantities in ep DIS data

The point of distance of closest approach is well describedTracking quantities are well described

Current Projects in the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) MaxMax--Planck Intitute MunichPlanck Intitute Munich, 09/05, 2005 - 14

D+: charm tagging with the MVDDD++: charm: charm taggingtagging with the MVDwith the MVD

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

Submitted to ICHEP2004

Current Projects in the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) MaxMax--Planck Intitute MunichPlanck Intitute Munich, 09/05, 2005 - 15

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

Q2 = 160 GeV2

pt(D+)=5.1 GeV

Current Projects in the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) MaxMax--Planck Intitute MunichPlanck Intitute Munich, 09/05, 2005 - 16

Charm semileptonic decays in DISCharm semileptonic decays in DISCharm semileptonic decays in DIS

Charm tagging:• detect charmed mesons BR(c→D*) = 2.6 % • detect e- BR(c→e-) = 9.6 %

Q2

Electron tagging using:• CAL clusters with a matched track & dEdx CAL deposit requirement•EEMC/ETOT>0.9 ("electron sample")•EEMC/ETOT<0.4 ("hadron sample") → Estimate background

Current Projects in the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) MaxMax--Planck Intitute MunichPlanck Intitute Munich, 09/05, 2005 - 17

Charm semileptonic decays in DISCharm semileptonic decays in DISCharm semileptonic decays in DIS

HERA-I 99-00 data

Results to be made preliminary for EPS05

Current Projects in the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) MaxMax--Planck Intitute MunichPlanck Intitute Munich, 09/05, 2005 - 18

Jet production in charged current DIS Eur.Phys.J.C31: 149-164, 2003

Jet production in charged current DIS Jet production in charged current DIS Eur.Phys.J.C31: 149Eur.Phys.J.C31: 149--164, 2003164, 2003

Test flavour changing electroweak theory and QCD in one type of events

Current Projects in the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) MaxMax--Planck Intitute MunichPlanck Intitute Munich, 09/05, 2005 - 19

Jet Substructure: mean subjet multiplicityJet Substructure: mean subjet multiplicityJet Substructure: mean subjet multiplicity

NC CC

The kT algorithm is reapplied to particles assigned to jet until distances between clusters:

( )2jetTcutij Eyd >

QCD does not distinguish if W (CC) or γ (NC) is exchanged(th.)(syst.)(stat.)0.0052 0.1202)(Mα 0.0065

0.00530.00600.0019ZS

+−

+−±=

HERA physics is excitingbut the LHC is calling ...