hera-b results on heavy quark production in p-a collisions

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HERA-B results on heavy quark production

in p-A collisions at 920 GeVWorkshop on Heavy Quark Physics at HERA-II

Weizmann Institute of Science, Rehovot, Israel, October 19-22, 2003

Boris Fominykhfor the HERA-B Collaboration

ITEP, Moscow

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Workshop on Heavy Quark Physics at HERA-II, Boris Fominykh - ITEP, Moscow 2

�� Contents

HERA-B Detector

Triggers and Data Samples

Selected Physics Topics with Interaction Trigger

Physics Topics with Di-lepton Trigger

Concluding Remarks


��

P - beam

Y (cm)

Z (cm)

X (cm)

C

Pd

CC

Ti

Ti

W

Al

Wire TargetsReconstructed primary vertices

Eight wires are in the halo

of proton beam.Wires are moved

to provide the constant

interaction rate.Data are collectedwith one or twooperated wires.Different wirecombinations

were usedin 2-wire runs.

!


��

The HERA-B Detector

Silicon Vertex Detector

Wire Target

MagnetRICH

Inner / Outer Tracker

ECAL

Muon Detector

0 m10 m20 m

Top View

electrons

920 GeV/cprotons

Spectrometer has geometrical coverage 15 - 220 mrad


�� HERA-B triggers

Data samples are collected with two types of trigger:1. Soft interaction trigger which demands

the minimum energy deposition in ECAL or minimal number of RICH hits to reject event without interactions.

2. Hard di-lepton trigger which selects events with two muons or electrons.


�� !

The Di-Lepton Trigger

Pretriggers: do track seeds using ECAL clusters or hit coincidences in Muon Detector (hardware)

First Level Trigger (FLT): provides hardware tracking in the tracking detectors behind magnet

Second Level Trigger (SLT): software tracking in the region of pretrigger and FLT track, track refit, extrapolation to Vertex Detector, vertex fit (PC farm)

DAQ: data is read out and buffered in pipe-line(proton bunches cross every 96 ns)

10 MHz

3 MHz

20 kHz

100 Hz

Full Event Reconstruction on PC farm Tape15%

85%


"# $%&

Collected Data Samples1. HERA-B commission in the year 2000:

di-lepton trigger provided 25 – 30 per hour,collected nearly 9,000 in electron andmuon channels.

2. Data taking November 2002 – February 2003:di-lepton trigger – 1000 – 1500 per hour, targets C, Ti, Wcollected nearly 200,000,000 minimum bias eventsand more 300,000 in electron and muonchannels.

J/ψJ/ψ

J/ψ

J/ψ


'( )*+Selected Physics Topics

with Interaction Trigger

J/� => µ+µ-

D+/D0

1. Cross section

2. Cross section ratio

Statistics was collected on C, Ti, W targets.


,- ./0Cross Section

N

J/� => µ+µ-

Mass µ+µ- (GeV/c2)

NJ/� = 90 ± 13 � = 40 MeV Mass = 3.086 GeV

C+Ti+W

Selection:muon ID + vertex fit

J/� production cross sectionused as a reference for severalHERA-B physics topics.Interaction trigger gives theopportunity to measure thiscross section with minimalcorrections and to decreasethe systematical error. Analysis ongoing.


12 345

D+/D0 Cross Section RatioD+ => K-

�+�

+ D0 => K-�

+

N N

mass (GeV/c2) mass (GeV/c2)

N = 122 ± 16 � = 25 MeV mass = 1.868 GeV

N = 137 ± 20 � = 26 MeV mass = 1.863 GeV

xF region -0.1 ÷ +0.05

D-meson selection:particle ID + detached vertexanalysis

+ c.c. + c.c.

HERA-B expects the statisticalerror about 20%, analysis ongoing.


67 89:

1. Production ratio of 2. differential distributions. 3. Diffractive charmonium production. 4. A-dependence of charmonium production5. production 6. bb production cross section.7. production.8. Upper limit on Br( )

Physics Topics withDi-lepton Trigger

J/�

�c

J/� and �(2S)

�

D0 => ��


;< =>?

�(�(2S)) / �(J/ Production ratio R =

Ent

ries

per

33

MeV

Ent

ries

per

33

MeV

Invariant mass (GeV) Invariant mass (GeV)

�+�

- e+e-

80% of statistics,all targets

�+�

-

all targets

0.019 0.0030.016 0.002R (Carbon)

1617 1773005 225

100510 1036176753 558N(J/�) N(�(2S))

e+e-

R preliminary –no acceptance correction.

Analysis is going on.

�)

± ± ± ±

± ±


@A BCD

J/� pT Differential Distribution on

d�/dp2T = �·{1+(35·� Fit parametrization

Preliminary resultfor (GeV/c)<pT>

1.291.30W

1.221.22C

electronsmuons

·pT/256/<pT>)2}-6 Acceptance correction is applied.

electrons

pT < 4.5 GeV/c

Good agreement with E672/706 and E771


EF GHI

J/� xF Differential Distribution on

Fit parametrization d�/dxF=�·(1-|xF|)C Acceptance correction is applied.

electrons

-0.3 < xF < 0.1

HERA-B is unique experimentwhere the negative

range is accessible.xF

Analysis is going on


JK LMN

Diffractive Charmonium Production

Data: 86% of J/� => µ+µ- Carbon

Monte Carlo:1. PYTHIA for hard interactions

+ FRITIOF for underlying event,NO diffraction.

2. + diffraction – Soft Color Interactionmodel (SCI), works with PYTHIA A.Edin, G.Ingelman, J.Rathsman.Phys.Lett. B366 (1996) 371.


OP QRS

J/�

++-

Rapidity Gaps in Events with

N

++-

is a sum of pseudorapiditygaps on both

sides of J/�

Carbon

preliminary

Dots - dataRed line - MC w/o diffractionBlue line - SCI MC (+diffraction)



TU VWX

Parametrization:

�α can be determined from measurements with two materials

A-dependence of charmoniumproduction


YZ [\]

Preliminary Results: Muon Channel

HERA-B very preliminary

Targets – C and W fromthe same station, only25% of full statistics.Luminosity ratio is underinvestigation => normalizationto E866Ratio of efficiencies: MCwith full detector and triggersimulation.



^_ `ab

Raw Spectra α(xF)

Carbon

HERA-B very preliminary

Tungsten

Preliminary Results: Electron Channel


cd efg

Data 2000Phys.Lett. B561(2003) 61

N(�c) - 380 ± 74

�c / J/� production ratio

�c / J/� 0.32 ± 0.07 ratio

�c => J/�� => ��, ee�Data 2002/2003

N(�c) nearly 9000 Shape of background is

under investigation.


hi jkl

z

Measurement of the bb ProductionCross Section

Data 2000

Method – detached vertexanalysis to separate B signalfrom direct J/ background

( and impact parameter cuts) �

Results are published in Eur.Phys.J. C26 (2003) 345

�(b=>J/�(��/ ee)X) = 32+14+6-12-7

nb/nucleon


mn opq

Measurement of the bb ProductionCross SectionData 2002/2003

Detached J/ search on 40% of the full statistics.�


rs tuv

��

C + W

ee � �� data � MC

� Cross Section Measurement

Consistent:

N N

C + W

35 11200 MeV160 MeV

33 7146 MeV146 MeV

Y eventswidth (MC) width (data)��

wx yz{

ee

Invariant mass (GeV) Invariant mass (GeV)

ee

± ±


|} ~��Upper Limit on Branching of

FCNC decay

whereis a ratio of the number of observed (confidence level)over the number of observed decaysis a ratio of the acceptance and efficiency over the

acceptance and efficiencyis a ratio of the production cross section over the

production cross section

J/� => �� used as a reference channel.The upper limit is calculated using the followingformula:

Br(D0 =>��) < Br(J/� => ��) RN Reff RCS

RN

Reff

RCS

D0

J/� J/�

J/�

D0

D0

D0 => ��


��

D0 real data in region

invariant mass (GeV)�+�-

N

signalregionside

band 1side

band 2

Br( )D0 => �� < 2.3*10-6

The systematic errors not taken into account

The result is comparablewith the recent result of CDF

and is better thecurrent PDG value

Preliminary

Upper Limit on Branching ofFCNC decay D0 => ��

4.1*10-6


��

Conclusions

HERA-B finished data taking and collected data samples sufficient for many interestingphysical topics.The advantage of HERA-B is the wide acceptanceand a good particle identification.Ongoing analysis is in the stage of cut optimization and detailed comparison of datawith MC.Preliminary physical results are expected at the beginning of the year 2004.

hera-b results on heavy quark production in p-a collisions

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