zeus status report | recent results and progress prc, desy

27th May 2004

ZEUS Status Report — Recent Results and Progress

PRC, DESY

Richard Hall-Wilton (University College London)

XY View ZR View

Zeus Run 48283 Event 11969 date: 28-02-2004 time: 09:51:54ZeV

is

E=161 GeV =109 GeVtE =53.1 GeVzE-p =27.1 GeVfE =134 GeVbE=0 GeVrE =2.62 GeVtp =2.07 GeVxp =1.61 GeVyp =108 GeVzp

phi=0.66 =-2.28 nsft =-2.04 nsbt =1.66 nsrt =3.5 nsgt

=73.2 GeVeE =0.84eθ =0.64eφ =0.12e,DA

x =0.56e,DA

y2=6757 GeV

e,DA2Q

Q2 = 6677 GeV2

• Running Conditions

• Detector Status

• Results from RecentData

• Physics Highlights

• Summary1

PRC ZEUS Status Report

ZEUS Background levels

• At the last PRC the extrapolated back-

grounds 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!

27th May 2004 2 Richard Hall-Wilton, UCL


Luminosity since the last PRC

• HERA delivered 51 pb−1

• ZEUS taken 22 pb−1

. A closer look at the efficiency

0

10

20

30

40

50

0 25 50 75 100 125 150 175 200

HERA delivered

ZEUS gated

running dayIn

teg

rate

d L

um

ino

sity

(p

b-1

)



Luminosity Delivered per Week

• ZEUS efficiency started at ∼ 40%

• Presently 50 - 60%

• CTD HV required to be on for data taking

0200400600800

10001200140016001800

5 10 15 20 25 30

ep runso.k. ep runs

week

lum

ino

sity

(n

b-1

)

0

0.2

0.4

0.6

0.8

1

5 10 15 20 25 30week

ph

ysic

s/al

l gat

ed

0

500

1000

1500

2000

2500

3000

3500

4000

5 10 15 20 25 30

HERA delivered

ZEUS gated

week

lum

ino

sit

y (

nb

-1)

0

0.2

0.4

0.6

0.8

1

5 10 15 20 25 30

week

ZE

US

/HE

RA

Spiky

Background 2000

2000

delivered

2000

gated

• Nearly all data taken can be

used for physics



ZEUS Efficiency — Examples of good and bad fills

• Fills from Last Week

• Bad Fill

. ZEUS Efficiency - 47%

. Regular trips

.Half way through the fill CTD

became inoperable

• Good Fill

. ZEUS Efficiency - 68%

. Occasional Trips

. DAQ Deadtime (15%

beginning of fill, 5% later)

. Occasional DAQ glitches

. Loss before detector is on

CTD CURRENT

HERA DELIVERED LUMINOSITY

ZEUS GATED LUMINOSITY

More typical since last weekend



ZEUS 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



Luminosity Monitor Upgrade — 6m Tagger Status

• Necessary to achieve 1% precision

. γ-Cal energy calibration

. Spectrometer acceptance calibration

• Rebuilt and installed in November

• Data in coincidence with Spectrometer:

. Energy sum within 1%

• Final integration with γ calorimeter trigger

ongoing

beam energy / GeV0 1 2 3 4 5 6

E /

E∆

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

∆EE = 16.5%√

E⊕ 5%

sum0_histxEntries 64827Mean 26.74RMS 2.6Constant 30.0± 5152 Mean 0.01± 27.27 Sigma 0.01± 1.82

spec + tag6 energy/GeV10 15 20 25 30 350

1000

2000

3000

4000

5000

sum0_histxEntries 64827Mean 26.74RMS 2.6Constant 30.0± 5152 Mean 0.01± 27.27 Sigma 0.01± 1.82

energy sum for tag6 energy > 4 GeV



Micro Vertex Detector

• No evidence of significant radiation dam-

age during routine HERA operation

. Mean signal size stable (S/N 12)

. Uncontrolled Proton beam loss

(4 Nov) caused 10% drop in signal

. Enormous effort from HERA to re-

duce this risk (exp. < 1 to end of HERA)

. Noise shows shallow slope

. Corresponds to 6 kRad in 500 days

on innermost cylinder

. 25 kRad expected by end of HERA II

. Front End Chips tested to 300 kRad

. Do not expect major damage from

radiation

• Detector in good shape

. Bad channels stable< 2%

. First physics results using MVD ...



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

24



Recent Data — STT Tracking

ZR View ZR View


is

E=8.73 GeV =2.58 GeVtE =0.558 GeVzE-p =8.07 GeVfE =0.654 GeVbE=0 GeVrE =0.255 GeVtp =-0.234 GeVxp =0.1 GeVyp =8.17 GeVzp

phi=2.74 =0 nsft =0 nsbt =0 nsrt =0 nsgt

• Selecting low multiplicity events from Data to tune the Monte Carlo

• STT matching with CTD and MVD found tracks ongoing



Recent Data — Neutral Current

ZEUS

1

10

10 2

10 3

103

104

Q2 DA

(GeV2)

Eve

nts

10

10 2

10-3

10-2

10-1

1xDA

Eve

nts

1

10

10 2

10 3

0 1 2 3

θe (rad)

Eve

nts

0

500

1000

1500

2000

0 1 2 3

ZEUS NC (prel.)03-04 (6.7 pb-1)

Q2 > 200 GeV2

NC MC(DJANGOH)

γh (rad)

Eve

nts

1

10

10 2

10 3

0 20 40 60 80 100

PT, h (GeV)

Eve

nts

0

500

1000

-40 -20 0 20 40

ZVTX (cm)

Eve

nts

• Neutral Current, Q2 > 200 GeV2

.∼15000 events for 6.7 pb−1

. 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



Recent Data — J/ψ and D? Production

• ∼ 2000 J/ψ Candidates →

M (GeV)∆0.14 0.145 0.15 0.155 0.16 0.165 0.17

Co

mb

inat

ion

s

0

50

100

150

200

250

300

350

ZEUS

+ (c.c)+π+π-K→+D*-1Luminosity = 10 pb

) > 3.0 GeV±(D*TP

58±) = 1242 ±N(D*2003-2004 Data

M (GeV)∆0.14 0.145 0.15 0.155 0.16 0.165 0.17

Co

mb

inat

ion

s

0

50

100

150

200

250

300

350

M (GeV)∆0.14 0.145 0.15 0.155 0.16 0.165 0.17

Co

mb

inat

ion

s

0

50

100

150

200

250

300

350

• ∼ 1240 D? Candidates

800

200

400

600

0

1000

32 2.25 2.5 2.75 3.25 3.5 3.75 4GeV)µµM(

2003−4 Data15 pb−1

Can

did

ates

• CTD performance is good

• Tracking using MVD + CTD

• Tracking working well



Recent Data — D+ Signal

• Use the MVD to tag secondary vertices from charm:SP

D+

K

π

π

−

+

+

) (GeV)ππM(K1.7 1.8 1.9 2 2.1

Co

mb

inat

ion

s

0

500

1000

1500

2000

)-1

ZEUS (prel.) 03-04 (5pb

ZEUS

+ (c.c.)+π+π- K→+D

) (GeV)ππM(K1.7 1.8 1.9 2 2.1

Co

mb

inat

ion

s

0

50

100

150

+ (c.c.)+π+π- K→+D

24±) = 86 ±N(D

> 5.0Lσ

L

ZEUS

)-1

ZEUS (prel.) 03-04 (5pb

Fit

• Can define a significance of seperation of

secondary and primary vertices:

~L = ~S − ~P

• No signal visible before

• Signal enhanced by cutting on signifi-

cance parameter → Encouraging!27th May 2004 13 Richard Hall-Wilton, UCL


Recent Data — Charged Current

XY View ZR View


is

E=88.5 GeV =48.2 GeVtE =25.1 GeVzE-p =35.4 GeVfE =53.2 GeVbE=0 GeVrE =44.7 GeVtp =24.6 GeVxp =-37.3 GeVyp =63.4 GeVzp

phi=-0.99 =5.29 nsft =-8.51 nsbt =6.24 nsrt =11.9 nsgt

=2.14 GeVeE =1.12eθ =-1.31eφ =0.09e,DA

x =0.47e,DA

y2=4155 GeV

e,DA2Q

Q2 = 3433 GeV2, /PT = 45 GeV



Polarised Charged Current Cross Section

• Charged Current cross section from Oc-

tober 03 - March 04 Data

. Right-handed e+ polarisation

. Average +33% polarisation

. Preliminary result for Moriond EW

• Cross Section for Q2 > 400 GeV2:

σcc

= 38.1 ± 2.1 (stat.) ± 0.8 (sys.)

± 2.0 (lumi.) ± 0.8 (pol.) pb

. Cross section above unpolarised value

. In agreement with standard model

Spin direction was changed 1 April

0

10

20

30

40

50

60

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

ZEUS

ZEUS (prel.) e+p 03-04 (6.6 pb-1)

ZEUS e+p 99-00 (P=0)

SM (CTEQ6D)

σCC

(Q

2 > 4

00 G

eV2 )

(pb)

PσC

C/σ

CC

SM(P

=0)

0.5

1

1.5

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1



Recent ZEUS Physics Output

• 12 new papers since last PRC →• DIS04: 15 new preliminary results

• 55 abstracts submitted to ICHEP

. 4 abstracts on HERA II data

• Have a look at some of the highlights

from recent results now ...

1. Instantons

2. Beauty photoproduction at HERA

3. High Q2 Neutral Current Cross Sections in e+p DIS at root(s)=318 GeV

4. Search for Contact Interactions, large extra dimensions, finite quark radius

5. Photoproduction of D* Mesons associated with a Leading Neutron

6. 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

10. Evidence for a narrow baryonic state decaying to Ks (anti)proton

11. Beauty in DIS

12. Substructure dependence of jet cross sections and determination of alphas



Strange Pentaquarks

1.45 1.5 1.55 1.6 1.65 1.70

50

100

150

200

250

300

350

M (GeV)

1.45 1.5 1.55 1.6 1.65 1.7

Co

mb

inat

ion

s / 0

.005

GeV

0

50

100

150

200

250

300

350

ZEUS 96-00FitGaussianBackgroundARIADNE MC

ZEUS

2>20 GeV2Q

)p p(S0K

/ ndf =35 / 44 2χ

1.5 MeV±peak= 1521.5

1.6 MeV±width= 6.1

48 ±events=221

1.45 1.5 1.55 1.6 1.65 1.70

20

40

60

80

100

120

140

160

180

200

pS0K

p S0K

• Accepted by Phys. Lett. B

• Select p K0s combinations

• Peak at 1521.5 ± 1.5 +2.8−1.7 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



Pentaquark searches

ZEUS

)(GeV)πΞM(1.4 1.6 1.8 2 2.2 2.4 2.6 2.8

En

trie

s / 7

.5M

eV0

20

40

60

80

100

120

140

160

180

anticipated NA49 signal

ZEUS (prel.) 96-00

Fit

34±candidates=1621.4 MeV±peak=1533.5

2.4 MeV±=7.6σ

2>1 GeV2Q

(1530)0Ξ

• NA49 report resonance in Ξ0πat 1.862 GeV

. Signal / Ξ0(1530) ∼ 6 - 8

• ZEUS sees no evidence of a signal

. Clearer Ξ0(1530) signal

. Larger statistics and smaller background



Charm Pentaquark SearchZEUS

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

0.14 0.15 0.16

M(Kππs) - M(Kπ) (GeV)

Com

bina

tions

/ 0.

5 M

eV

ZEUS (prel.) 1995-2000(126.5 pb-1)

backgr. wrong charge

N(D*±) = 42730 ± 350

• H1 has reported resonance at 3.1 GeV in M(D?p)

. Interpreted as charmed pentaquark

• Search by ZEUS shows no evidence for signal at 3.1 GeV

. Inclusive D? sample ∼ 43000

. DIS D? sample ∼ 9700

ZEUS

0

20

40

60

80

100

2.95 3 3.05 3.1 3.15 3.2 3.25 3.3

M(D∗p) = ∆Mext + M(D∗+)PDG (GeV)

Com

bina

tions

/ 10

MeV

ZEUS (prel.) 1995-2000 (126.5 pb-1)

P(p) < 1.35 GeV,

dEdx(p) > max(1.3,0.3/P(p)2+0.8)

fit: A (∆Mext-mp)B exp[-(∆Mext-mp)C]

fake signal of 0.3% from N(D∗±)

ZEUS

0

20

40

60

80

100

120

140

2.95 3 3.05 3.1 3.15 3.2 3.25 3.3

M(D∗p) = ∆Mext + M(D∗+)PDG (GeV)

Com

bina

tions

/ 10

MeV

ZEUS (prel.) 1995-2000 (126.5 pb-1)

P(p) > 2 GeV, dEdx(p) < 1/P(p)2+1.2

fit: A (∆Mext-mp)B exp[-(∆Mext-mp)C]

fake signal of 0.4% from N(D∗±)

• Gaussian shows

expected signal for

N(Θ0c)/N(D?) = 1%



Beauty Production at HERA

• Papers published on beauty pro-

duction in DIS and PhP

. PhP: subm to Phys. Rev. D

. DIS: subm to Phys. Lett. B

• PhP result:

. Good agreement with NLO

1

2

3

4

5

6

7

8

1 10 102

Q2 [GeV2]

Dat

a / T

heor

y

b Cross Sections at HERA

ZEUS σvis(jjµX) prelT -1.6 < ηµ < -0.9, pµ > 2.5 GeV

ZEUS σvis(jjµX) prelT -0.9 < ηµ < 1.3, p

µT > 2.5 GeV

ZEUS σvis(jjµX) prelT 1.48 < ηµ < 2.3, pµ > 4 GeV, p

µT > 1 GeV

H1 σvis(jjµX) Imp.-Par.⊗ prelT (prel.)

H1 σvis(ejµX) Imp.-Par.⊗ prelT (prel.)

ZEUS σvis(ejµX) prelT

NLO QCD

∫∫

ZEUS

10-1

1

10

10 2

10 3

0 5 10 15 20 25 30

ZEUS 96-97 b→e

ZEUS 96-00 b→µ

NLO QCD

pT b (GeV)

dσ/

dp

T b

(p

b/G

eV)

dσ/dpT(ep→ebX)dσ/dpb

Q2<1GeV2 0.2<y<0.8

|ηb|< 2

• DIS result - 1st publication on this topic

• HERA I message on beauty production:

Good agreement between data and NLO pQCD



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)2

. Data distinguishes between PDF fits

. Clear sensitivity to the gluon

. Need NLO to be able to constrain the

gluon with the data

ZEUS

10-2

10-1

1

10

10 2

102

(a)

W (GeV)

σ(γ* p→

J/ψ

p) (

nb)

ZEUS PhotoproductionZEUS DIS 98-00

Q2 (GeV2)

0.

0.4

3.1

6.8

16.

(× 1)

(× 0.2)

(× 0.1)

(× 0.05)

(× 0.03)

1

10

10 2

10-1

1 10 Q2 (GeV2)

σ(γ* p→

J/ψ

p) (

nb)

0//

//

MRT (ZEUS-S) × 1.49MRT (CTEQ6M) × 2.22MRT (MRST02) × 2.98

< W > = 90 GeV

(b)

0

1

2

0 5 10 15Q2 (GeV2)

δ

σ ∼ Wδ



Charged and Neutral Current DIS Cross Section Measurements

10-7

10-6

10-5

10-4

10-3

10-2

10-1

1

10

103

104

ZEUS

ZEUS e+p CC 99-00

ZEUS e−p CC 98-99

SM e+p CC (CTEQ6D)

SM e−p CC (CTEQ6D)

ZEUS e+p NC 99-00

ZEUS e−p NC 98-99

SM e+p NC (CTEQ6D)

SM e−p NC (CTEQ6D)

Q2 (GeV2)

dσ/

dQ

2 (p

b/G

eV2 )

• Charged and Neutral Current

Cross sections for e+p and e−p

published

• Above Q2 ∼ 10000 GeV2

. Electroweak Unification

• Standard model - excellent de-

scription of the data

• Complete picture from HERA I

. Use this data in QCD fits



New QCD Fits

• Add high Q2 data into ZEUS-

Only structure function fit

. Full ZEUS HERA I data set

. All 94-00 e±p Data

• Compare to published ZEUS-S

. Include Fixed target data

. 94-98 ZEUS Data

• Good agreement

. ZEUS-Only Fit still needs

additional constraint for x> 0.1

. HERA II Data at high x

. Use jets data in the fit



Adding ZEUS Jet Data to QCD Fits

• Very precise jet data from ZEUS

• Include ZEUS jet data in QCD fits

. Rigorous

. Inclusive DIS jet data

. High ET dijet PhP Data (xγ >0.75)

• Compare ZEUS-Only fit with + without jet

data

. Jet data constrain gluon at medium x

. Improved precision at high x

ZEUS-O (prel.) 94-00 uncorrelated error correlated error

2 = 10 GeV2Q

10-4

10-3

10-2

10-1

1

ZEUS-JETS (prel.) 94-00

2 = 10 GeV2Q

10-4

10-3

10-2

10-1

1

2 = 100 GeV2

Q

10-4

10-3

10-2

10-1

1

2 = 100 GeV2

Q

10-4

10-3

10-2

10-1

1

2 = 1000 GeV2

Q

10-4

10-3

10-2

10-1

1

2 = 1000 GeV2

Q

10-4

10-3

10-2

10-1

1

10-4

10-3

10-2

10-1

110-4

10-3

10-2

10-1

1

10-4

10-3

10-2

10-1

110-4

10-3

10-2

10-1

1

10-4

10-3

10-2

10-1

110-4

10-3

10-2

10-1

1

0

10

20

30

0

10

20

30

0

10

20

30

-0.2-0.1

00.10.2

-0.2-0.1

00.10.2

-0.2-0.1

00.10.2

x

xg

ZEUSZEUS-O ZEUS-JETS



Adding ZEUS 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 1%

10 15 20 25 30 35 40 45

10-3

10-2

10-1

1

10

102

103

104

105

106

107

(GeV)BT,jet

E

(pb

/GeV

)B T

,jet

/dE

σd

ZEUS 96-97 (DIS data) Jet Energy Scale Uncertainty

: 0Zδ × hadδ × NLO QCD

ZEUS-JETS (prel.) 94-00 total uncertainty

2 < 250 GeV2125 < Q

2 < 500 GeV2250 < Q

2 < 1000 GeV2500 < Q

2 < 2000 GeV21000 < Q

2 < 5000 GeV22000 < Q

2 > 5000 GeV2Q

)5 10×(

)4 10×(

)3 10×(

)2 10×(

10)×(

1)×(

10 15 20 25 30 35 40 45

10-3

10-2

10-1

1

10

102

103

104

105

106

107

ZEUS



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 for events with 1 broad

jet, 1 narrow jet

• Dominant diagrams cosθ?± 1 different

. Positive-negative assymetry

. +1 — t-channel gluon exchange

. -1 — u-channel quark exchange

• QCD subprocesses separated for first

time

• subm. to Nucl. Phys. B

ZEUS

0

1

2

3

4

5

6

7

8

9

10

-0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8

ZEUS 98-00 γp (broad-narrow jets)

PYTHIA

jet shape selection

cos θbroad

*

dσ/

cos

θ broa

d

*

(arb

itra

ry u

nits

)

q g

g q

q

q q

g

g g



αs Measurements from ZEUS

• Large number of αs measure-

ments from ZEUS

. Compatible with world aver-

age

. World average does not in-

clude ZEUS measurements

. Individual measurements

competitive with world average

th. uncert.

exp. uncert.

World average (S. Bethke, hep-ex/0211012)

Dijet cross sections in NC DIS ZEUS (Phys Lett B 507 (2001) 70)

Inclusive jet cross sections in NC DIS ZEUS (Phys Lett B 547 (2002) 164)

NLO QCD fit ZEUS (Phys Rev D 67 (2003) 012007)

Jet shapes in NC DIS ZEUS (DESY 04-072 - hep-ex/0405065)

Subjet multiplicity in NC DIS ZEUS (Phys Lett B 558 (2003) 41)

Subjet multiplicity in CC DIS ZEUS (Eur Phys Jour C 31 (2003) 149)

Inclusive jet cross sections in γp ZEUS (Phys Lett B 560 (2003) 7)

0.1 0.12 0.14αs(MZ)



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 H1 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 View ZR ViewQ2 ∼ 12000 GeV2


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