HERA-B results 1

HERA-B results

Università and INFN – Bologna

From the HERA-B Collaboration

HERA-B results 2

HERA-B:IHEP, BeijingU. Tsinghua

NBI, Copenhagen

U. Humboldt, BerlinU. DortmundDESYMPI HeidelbergU. HeidelbergU. MannheimMPI MunichU. RostockU. SiegenDESY Zeuthen

INFN, U. Bologna

U. UtrechtNIKHEF

U. Oslo

LIP, U. CoimbraLIP, U. Lisbon

ITEP, MoscowJINR, Dubna

J.F. Inst, Ljubljani

U. Barcelona

U. Zurich

INR, Kiev

U. Texas, AustinU. CincinnatiWayne State U.U. HoustonU. Calif, Los Angeles

China

Denmark

Germany

Italy

Netherlands

Norway

Portugal

Russia

Slovenia

Spain

Ukraine

USA

Switzerland

13 Nations30 Institutes 150 physicists

HERA-B results 3

10 m

The HERA-B Detector

Magnet

Muon Detector4 layers of gas pixel

chambers (inner) and MWPC with cathode pad

readout (outer), pad-coincidence pretrigger

0 m20 m

Top View

920 GeV/c Protons

Inner / Outer Tracker7 layers of GEM-MSGCs (inner) and honeycomb drift chambers (outer)

Wire Target 2 stations, 4 wires

each (C, Ti, W)

Silicon Vertex Detector

8 double-layers of double-sided Si-microstrips

RICHC4F10 radiator,

multianode PMT focal plane

ECALW/Pb-scintillator

sampling shashlik calorimeter, cluster

pretrigger

e+/e- beam

HERA-B results 4

Si

gas

had to face LHC equivalent particle flux 10 ears in advance.

exploring a new regime of radiation load, particle flux, event rates...

detectorstrigger systemDAQ

At forefrontof technology

HERA-B results 5

The HERA-B detector p-Nucleus interactions at 920 GeV BX crossing rate: 10 MHz Up to 4•107 interactions/s (~5ev/bx)Very sophisticated and challenging detector.Large central acceptance ( 5 > lab > 2 )Capability to reconstruct the full eventVery good particle ID for (e, , , K, p)High resolution vertexingTarget: 8 wires in the p-beam halo 5 materials: C, Ti, Al, Pd, WDouble wire configuration for A-Dependence Measurements: C+WOnline event reconstruction Very selective multilevel trigger (hardware + software) J/ μμ/ee

S=41.6 GeV

p-beam

z [cm]

12C

48Ti

184W

Suitable for P-Nucleus interaction studies

HERA-B results 6

Electromagnetic Calorimeter (ECAL)

Main Italian responsibilities: readout and pretrigger electronics Second Level Trigger and reconstruction codes Detector calibration and maintenance

INFN contribution (Bologna)

HERA-B results 7

Multilevel trigger scheme based on Kalman filter.

5 (10) MHz

20 KHz

100 Hz Full online reconstruction and logging to tape

Pretrigger/Level 1(rejection ~250)

Level 2(rejection. ~200)

(<12 s)

(5-10 ms)

(~1s)

Two PC-Linux farms used in L2 and for the offline reconstruction.

Trigger & DAQ System

•150 M di-lepton trigger events (e+e-/μ+μ- triggers) 300 000 J/ψ (>1000 per hour) 15 000 c1+ c2

5 000 ψ(2S)

• 210 M minimum bias events1000 ev/s >1TB/day

• 35 M hard photon events

• 60 M “glueball” trigger events

Data taking finished in 2003.

Electrons

~ 108,000 J/

σ = 64 MeV/c2

/ ~ 1600 (2S)

Main data samples

HERA-B results 9

Dilepton spectrum: Muon Channel

Approx. 177,000 events

Mass: 3095 MeV/c2

Width: 44 MeV/c2

J

Approx. 3,500 events

Mass: 3674 MeV/c2

Width: 53 MeV/c2

s

Low-mass region:

High-mass region:

1S

2S/3S

HERA-B results 10

Physics topics

Main physics topics addressed: FCNC D0 μμ Br limit bb cross section production J/ production

J/: pT distribution

J/: xF distribution

J/: A-dependence (2s) production

c/J/ production ratio

Open charm production Pentaquark production

e+ e-

+ -(2s)

bb

(1-3s)

J/

D0

C

MB data

D0

Di-lepton trigger

K()

HERA-B results 11

Current limits by :

•CDF: BR(D0+) < 2.510-6 (90% CL) Phys. Rev. D68 (2003) 091101

•BaBar: BR(D0+) < 1.310-6 (90% CL) hep-ex/0408023

New Limit on BR(D0+)

• Search for flavor-changing neutral current decay D0+

(branching fraction enhanced in some MSSM models ~10-7)

• 3 events in signal region:

Phys.Lett.B596:173-183,2004

BR(D0+) < 2.010-6

(90% CL)

18 events 6 events3 evtc

u

μ+

μ-

W+

W-

νμ

d,s,b

BR from SM: ~10-19

HERA-B results 12

σ(bb): inclusive b production

pA bb X b J/ψ Y e+e-/+- Y

upstream ℓ+

J/ψ

b

Y

ℓ-

IW

Δzp

downstream

B Meson has a long life time ( ~ 9 mm at HERA-B kinematics)~ 0.5 mm dilepton vertex resolution

J/ from a B decay will be detached from primary interaction

Normalization on the inclusive prompt J/ cross section. Systematic error minimization

Analysis cuts:- Decay lenght (Δz)- Impact parameter

HERA-B results 13

open b production• C,W,Ti targets• Full statistics• Unbinned likelihood fit

20% sys. error under investigation, main contribution: Br(bbJ/X) = 2.320.20%

0.027 0.004 0.005/

bb

J

Lifetime:

= (1.41 ± 0.16)ps

HERA-B results 14

Cross section obtained by using the fit based on NRQCD of J/ψ cross sections .

14.9 2.2 2.4 nb/nucleonbb

Cross section

Previous HERA-B result of year 2000 (~ 10 ev)[Eur. Phys. J. C26, 345 (2003)]:

+ +- -= 14 6

12 7bb( ) 32 nb/ Ns

• Theoretical uncertainties: – b quark mass 4.5 - 5 GeV– At NLO, scale ()

dependence• Previous measurements do not

agree between each other• Agreement with the previous

HERA-B result (1.5 σ)

Phys. Rev. D73 (2006) 052005

σ(b

b)

(nb

/nu

cle

on

)

Proton energy (GeV)

N. Kidonakis et al.HERA-BE789E771

R. Bonciani et al.

400 500 600 700 800 900 1000

1

10

102

HERA-B results 15

NA3

FNAL

FNAL

FNAL

FNAL

E605

E605

E772

E771

R-108

CERN

CCOR

HERA-B

pN + X, +-, e+e-

M(+-) (GeV/c2)

M(e+e-) (GeV/c2)

Drell-Yan

Comb. BG

0 /

/ /

( ) ( ) |1

( / )

y J

J J eff

dBr l l

ndyBr J l l n y

30.87.4stat

7514stat ee

0

( ) exp oo

y

mdBr s

dy s

Craigie parametrization

NLO calculation inside CEM (hep-ph/0311048)

Upsilon production

HERA-B results 16

μμ mass [GeV/c2]

μ+μ- 100 ± 12 C

Ti

W

σ pA =

σ pN ·A0.9

6

σ(p

AJ

/ψ)

[μb

]

A

s y stat syst(J/ )=(663 74 46 )nb/nucl± ±pN

for each target material(A = 12 [C], 48 [Ti], 184 [W])

/

( / / )Br J e ey m m

y

Ns

e

( )

( )( ) ( )y mm

+ - + -®+ - + -=

® × ×

A

J/ e eAJ/ A AL

inclusive measurement

used MB data to minimize trigger

systematics

J/ψ production cross section

Good agreement with the fit of J/ψ + ψ′ cross sections and ψ′/ψ production

ratios (29 results in all) in the context of NLO NRQCD (F. Maltoni)

p-pp-A

experimental data

sometimes inconsisten

t

HERA-B PHENIX

CERN-PS

WA39

IHEP

preliminary

HERA-B results 17

Electron channel: compared with p-A results (√s=38.8 GeV) agreement with muon channel in all distributions.

( )352562 T

T

621 p

dpd

ps -é ùµ + ×ê úë ûT< >p

[GeV-2/c2]

E789 (Au)E789 (Au)

HERA-B (C)HERA-B (C)

E771 (Si)E771 (Si)E672/E706 (Be)E672/E706 (Be)

pT [GeV/c]

2T

1 ddps

s

HERA-B (Ti)HERA-B (Ti)

HERA-B (W)HERA-B (W)

197

184

48

28

12

9

<p

T>

[GeV

/c]

T

ln0.021 0.003

d

d pA

= ±

<pT> grows logarithmicall

y with A:

C Si Ti AuWBe

A

J/ψ Differential Distribution: pT

HERA-B results 18

[(1 )(1 )] / ( )d d x x x xkµ - - +1 2 1 2Fxs/

( )2 2, J/

14 /

2x m sy= + ±1 2 F Fx x

Fitting curves:

with

first data produced at negative xF

E789E789 (Be, Cu)(Be, Cu)E789E789

(Be, Cu)(Be, Cu)

HERA-B (C-W)HERA-B (C-W)

E789E789 (Au)(Au)

E789E789 (Au)(Au)

E672/E706 (Be)E672/E706 (Be)

E771 (Si)E771 (Si) C

W

Ti

J/ Differential distribution: xF

Electron channel: compared with p-A results (√s=38.8 GeV) agreement with muon channel in all distributions.

HERA-B results 19

Measured in different reference systems (CS, GJ, HCM) and wrt pT and xF

Preliminary:[-0.3,0.0] ±0.1

GJ

pTxF

Also studied by CDF but at larger pT

angle perpendicular to

No experimental results important to study also

Hint for > 0

Same range as previous experiments

J/ polarization

Exp.Interaction & p-

momentum

E379 p-Fe @ 400 GeV 0.16 ± 0.08

E672/E706 p-Be @ 530 GeV 0.01 ± 0.15

E672/E706 p-Be @ 800 GeV -0.11 ± 0.15

E771 p-Si @ 800 GeV -0.09 ± 0.12

E866 p-Cu @ 800 GeV[+0.1 : -0.5]xf [0.3:0.9]

HERA-B results 20

J/ A-Dependence• Test of charmonium production models in

nuclear matter (nonrelativistic QCD + initial/final state interactions in nucleus)

pA pN ; /A N L

• Previous result of FNAL E866 extended to xF = –0.35

• Result from full +– sample, statistical uncertainties only, similar results for e+e-

HERA-B results 21

238

184

2819712

184

12

129 2764

108184

HERA-B cHERA-B cHERA-B cHERA-B c

HERA-B wHERA-B wHERA-B wHERA-B wE771E771E771E771

E789E789E789E789E705E705E705E705

NA38, NA38, NA50 & NA50 & NA51NA51

NA38, NA38, NA50 & NA50 & NA51NA51

[GeV]s

6

12

9

E331E331E331E331

E444E444E444E444

E288E288E288E288

B′σ

(ψ′)/B

σ(J

/ψ)

(%)

12

NA38NA38NA38NA38

p-A

(1.63 ± 0.07)% C

= (1.99 ± 0.24)% Ti

(1.62 ± 0.10)% W

HERA-B tiHERA-B tiHERA-B tiHERA-B ti

(2S) Production

R BR((2S) )(2S)

BR(J / ) J/

N(2S)

NJ/

J/

(2S)

• Measure (2S) cross section relative to J/ reduce systematic uncertainties

• No dependence wrt A and cms energy

• Competitive measurements

HERA-B results 22

( )( / )

B dBd J

s ys y

¢ ¢

E771 E771 NA50NA50NA50NA50

HERA-BHERA-B

HERA-B measurements extend the range of the previous results with comparable or better precision

E789 E789

xF

( )( / )

B dBd J

s ys y

¢ ¢

pT

NRQCD (p-p)NRQCD (p-p)

Fraction of J/ψ from ψ′: 0 0

0

J /J /J /J /

J / (7 )B

BB

R y p py p py hy p

yyy

yy r

+ -ìïïïïïíïïïïïî

+ -

+ -

®¢®¢

¢®¢= ´ × = .0±0.2±0.4 %l l

l lBRs

current PDG avg.: 1.03 ± 0.12

Constraint on the double ratio (test of lepton universality)

J / J /

BB

B Bm m

y yy m my

y y m m

r r+ -

¢ ¢

+ - + -+ -

+ - + -

®® ¢¢

® ®

= = 1.00±0.08±0.04e e e e

e e

(2Sdifferential distributions

HERA-B results 23

c Production

,

2

, J /1

J / J /

BR( J/ )( ) c i c

c

c iic

NR

N

Test of charmonium production models: fraction R(c) of J/ from radiative decays c J/ μ+ μ–

background: mixed events

Muon channel

En

trie

s (

10

MeV

/c2)

M(J/ ) – M(J/)

NRQCD

CSM

ECMS

R(

c)

Average

HERA-B results 24

Searched pentaquark states:

Θ+(1530, uudds) → pK0 (or nK+)

Ξ (ddssu) → Ξ π (or Σ K) → Λππ

MB data sample (~210M evts, 3 nuclear targets C, Ti, W) used to:

search for the reported pentaquark signals

provide upper limits on particle yield ratios (vs Λ(1520) and Ξ0(1530))

possibly determine physical quantities (width, spin, parity, charge) of pentaquarks for different final states (p-K0, -)

and charge c.

K-(us) or (uds)

K0

p

p

wire

+ (uudds)

Phys. Rev. Lett.93:212003,2004

Pentaquark Searches

First negative result based on high statistics and performed on two different states.

HERA-B results 25

+,-- signals

UL(95%)Bd/dy|y=0 = 4-16 b/N

@ 1521-1555 MeV/c2

+ / (1520) < 3 – 12 %

UL(95%)Bd/dy|y=0 = 2.5 b/N @ 1862 MeV/c2

-- / - < 3/B % -- / (1530)0 < 4/B %

B d

/d

y b

/C

B d

/d

y b

/C

Co

un

ts

C

ou

nts

NA49

HERA-B

UL(95%)

mass

1.4 1.475 1.55 1.625 1.7

pK0s mass

UL(95%)

mass GeV/c2

Phys. Rev. Lett. 93 (2004) 212003

HERA-B results 26

Kππ inv. mass [GeV/c2]

en

trie

s/(1

0

MeV

/c2)

en

trie

s/(1

0

MeV

/c2)

Kπ inv. mass [GeV/c2]

194 ± 20

92 ± 11

D± D*±D0+D0

m(Kππ)-m(Kπ) [GeV/c2]

en

trie

s/(0

.5 M

eV

/c2)

49 ± 10

| ( ) ( )| 50MeVm K mp - <0D

| ( ) ( )| 50MeVm K mp - >0D

p

N

D+ K -

p+

p+

0DK -

p+

p

N

p

N

0D

K -

p+

p++*D

proper decay length [μm]proper decay length [μm]

D0 D+

preliminarypreliminary

cτ = 292 ± 38 μmcτ = 125 ± 21 μm

dN/dz

[a.u

.]

agreement with PDG values

Open charm production: signals

HERA-B results 27

Imp

ort

ant

test

for

QC

D

preliminary -0.1 < xF < 0.05 full xF range

σ(DD00) [μb/nucl] 21.4 ± 3.2 ± 3.6 56.3 ± 8.5 ± 9.5

σ(DD++) [μb/nucl] 11.5 ± 1.7 ± 2.2 30.2 ± 4.5 ± 5.8

σ(DD*+*+) [μb/nucl] 10.0 ± 1.9 ± 1.4 27.8 ± 5.2 ± 3.9

σ(DD++)/σ(DD00) 0.54 ± 0.11 ± 0.14

σ(DD*+*+)/σ(DD00) 0.49 ± 0.12 ± 0.10

u d

D±/D0

√

u d

D*±/D0

√

0INCL INCL( )/ ( 0.326) 0.003D Ds s± ±= 0

INCL INCL( )/ ( 0.497 0.001)D Ds s*± ±=

0.43 0.09.avg ±=0.61 0.08.avg ±=

HERA-B prel.HERA-B

prel.

violated by about a factor 2

For Isospin symmetry and feeddown BRs,

expected

Open charm production: cross section