august 25 2005hernan wahlberg, hadron051/26 open and hidden beauty in 920 gev proton-nucleus...

August 25 2005 Hernan Wahlberg, HADRON05 1/26

Open and Hidden Beauty in 920 Open and Hidden Beauty in 920 GeV Proton-Nucleus CollisionsGeV Proton-Nucleus Collisions

Hernan WahlbergHernan WahlbergUtrecht University/NIKHEFUtrecht University/NIKHEF

For the HERA-B CollaborationFor the HERA-B Collaboration


OutlineOutline

• HERA-B detector• Reference prompt J/ sample

for beauty analysis• Open cross section ( ) production cross

section• Summary

bbbb


HERA-B Detector (I)HERA-B Detector (I)


HERA-B Detector (II)HERA-B Detector (II)

Fixed target detector at p ring HERA, DESYProton beam at 920 GeV/c (√s = 41.6 GeV)Interaction rate ~ 5 MHzWire targets (different materials: C,W,Ti) in proton haloMultiple trigger level (Hardware + Software) for lepton pairsHigh resolution vertexing (~ 500 m-longitudinal)Very good particle ID for e, , , K and p


Data SampleData Sample

HERA-B has finished data taking (March 2003)

Dilepton triggerPretriggers: high ET ECAL clusters, MUON hitsFLT (hardware trigger): track finding behind magnetSLT (software trigger): track finding behind magnet

and in silicon detector + vertex reconstruction

165 M dilepton triggered events ≈ 300.000 J/Ψ (>1000 per hour to tape)

3 target wires of different materials Carbon (A=12, ≈ 64% of total statistics) Titanium (A=48, ≈ 9%) Tungsten (A=184, ≈ 27%)


Reference Reference Prompt Prompt J/J/SampleSample

J/: 148200±500

’: 2600±120

J/: 103800±1000

’: 1700±160

Long tracks (vertex detector + tracking system) PID: likelihood , E/p Dilepton vertex probability > 1% J/ψ acceptance: -0.35 < xF < 0.15


OutlineOutline



section• Summary

bbbb


B: MotivationB: Motivation

Experiment E p (GeV) s (nb/ nucleon) N Events

E789 800 5 ± 1.5 ± 3 ~ 20

E771 800 43(+27-17)± 7 ~ 15

HERA-B(2002) 920 32(+14-12)(+6-7) ~ 10

Theory Order

N.Kidonakis et al. NLO + NNLL 30 ± 18

R.Bonciani et al. NLO + NLL 25 (+20-13)

Theoretical uncertainties: b quark mass 4.5 - 5 GeVProduction near energy threshold. At NLO, scale () dependence.

Need to go beyond NLO

Previous measurements:Poor statistical precisionIncompatible

HERA-B 2002 measurement


B: Selection MethodB: Selection Method

B Selection: (~ 40% Efficiency)Lepton impact to the wire Distance J/ to wire

pA bb + Xb(b) B J/ + X

J/ ; e+e-


B: Principle of MeasurementB: Principle of Measurement

)/(

1

)/(

)(

/ XJbbBrn

n

J

bbR

zBRJ

B

ss

s

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 Only needed to count detached J/

Measurement relative to direct J/ production to minimize trigger/reconstruction uncertainties R= relative efficiency1

B selection efficiency from MC


B: Data and MC SamplesB: Data and MC Samples

Good agreement between data and MC simulationGood separation between direct and detached J/


B: Detached J/B: Detached J/ (muons) (muons)

Detachment cuts (on significance) optimized blindly and simultaneously:

Δz > 9 σ Iwl > 2.6 σIwJ/Ψ < 9σ

Upstream Downstream

46.2+8.6-7.9-0.1±1.4

Upstream from target: unphysical region Downstream from target:

signal region Unbinned likelihood fit Background:

Combinatorial B doublesemileptonic

No prompt J/


B: Detached J/B: Detached J/ (electrons) (electrons)

Detachment cuts (on significance) optimized blindly and simultaneously :

Δz > 10 σ Iwl > 3.0 σIwJ/Ψ < 12σ

Upstream from target: unphysical region Downstream from target:

signal region Unbinned likelihood fit Background:

Combinatorial B doublesemileptonic

No prompt J/

Upstream Downstream

36.9+8.5-7.8-4.2±1.9


B: Sample Confirmation (I)B: Sample Confirmation (I)

Confirmation of B flavor: Long lived candidates around J/ψ massB lifetime compatible with expectations 1.54 ps (PDG)

= 1.39 ± 0.19 ps


B: Sample Confirmation (II)B: Sample Confirmation (II)

Search for additional tracks in a common vertex ( J/+h± )

Relax detachment cutsPartially independent sampleHigher purity but lower stat

RΔσ = (4.3±1.0)x10-2 compatible with main result (see next slide)

Some fully reconstructed final state eventsOngoing study based on double semileptonic bb decay sample

22 ± 5


B: Results (I)B: Results (I)

e and μ channels are partially independentResults agree well within errors

μ+μ- e+e- μ+μ-& e+e-

RΔσ (x10-2 )

in HERA-B acceptance

3.01 ± 0.57stat

3.60 ± 0.79stat

3.2 ± 0.5stat

Good control of systematics


B: Results (II)B: Results (II)

sysstatJ/ ψ

bbσ 0.0030.0040.027

σ

σR

eon1.4nb/nucl1.59.6σbb

σJ/Ψ = (352 ± 2 ± 26) nb/n (average E789-E771)

Weighted average with previous HERA-B measurement(I Abt et al., Eur. Phys. J. C26 (2003) 345)


Cross section in full xF range:

0.0030.0040.028σ

σR

J/ ψ

bbσ


B: Results (III)B: Results (III)

Ongoing study suggests ~40% higher σ(J/ψ) and consequently σ( )bb

Result compatible

with lower limit of theoretical predictions Compatible with E789



OutlineOutline



section• Summary

bbbb


: : MotivationMotivation

Test quarkonium production models Possible nuclear suppression ?

Several measurements available but unclear situation at √s ~ 40GeV

HERA-B has good coverage in the central region of collisions ( xF ~ [-0.35,0.15])

HERA-Bs = 41.6 GeV

E772 (A=2)

E605 (A=64)


: : MethodMethod

pA + X - ; e+e-

Measurement relative to prompt J/ Less sensitive to systematic effects

Prompt J/cross section from E771 and E789

eff

J/ψ

J/ψyΔyε

ε

N

Nσ(J/ψ))llBr(J/ψ

dy

dσ)llBr(

1

0


: : SignalSignal

Background:Random combinatorial: estimated by like sign pairs of real dataDrell-Yan: shape estimated from MC

(1S) / (2S) / (3S) relative production fixed to E605 results

30.8±7.4

75±14

+-

e+e-


: : Preliminary ResultsPreliminary Results

Events Br• ds/dyy=0

+- 30.8 ± 7.4 3.0 ± 0.7stat ± 0.6stat pb/n

e+e- 75 ± 14 4.7 ± 0.9stat ± 1.0sys pb/n

Both 3.5 ± 0.8 pb/n

Both channels are compatibleExtrapolation to √s = 38.8 GeV yields:Br• ds/dyy=0 = 2.3 ± 0.5stat ± 0.5sys pb/n

compatible with E605(more than 1 s) below E772 and E771

Based on σJ/Ψ = (352 ± 2 ± 26) nb/n (average E789-E771)


: Global Situation: Global Situation

As

ms

dy

dBr o

o

y

exp)(0

ss

Modified Craigie parameterization to include nuclear suppression (parameter Data compatible with no nuclear suppression:

= 0.96 0.05


Conclusions (I): B cross sectionConclusions (I): B cross section

HERA-B measured (2000+2004) Rσ = (2.8±0.4±0.3)x10-2

Lifetime of candidates in agreement with expectationsCompatibility between different channelsThe complete HERA-B sample (~90 events) is significantly larger than previous fixed target experiments Based on σJ/Ψ = (352 ± 2 ± 26) nb/n (average E789-E771)

Ongoing fit of existing experimental results on σ(J/) with COM parametrisation to provide absolute bb cross section



Conclusions (II): Conclusions (II): cross section cross section

Preliminary cross section measurement 3.5 ± 0.8 pb/n

In agreement with E605Global fit to data consistent with no nuclear suppression


Backup SlidesBackup Slides


P.NASON, QCD at High Energy, Proc. Of the XX Int. Symp. on Lepton and Photon Interactions at High Energies, hep-ph/0111024

P.NASON et al., Adv. Ser. Direct. High Energy Phys. 15(1998), 609

H1 Coll. T.Sloan et al., Proc. QCD 2001 Conf., Moriond, March 2001.ZEUS Coll. J.Breitweg et al., Eur.Phys.J.C18(2001)

L3 Coll. M.Acciarri et al., Phys.Lett.B503(2001) 10

OPAL Coll. OPAL Phys.Note PN455, August 29,2001

N. Kidonakis et al., Phys.Rev. D64 (2001) 114001-1

D.M.Jansen et al., Phys.Rev.Lett.74 (1995)3118

T.Alexopoulos et al., Phys.Rev.Lett.82 (1999) 41

R. Bonciani et al., Nucl.Phys.B529 (1998) 424

BIBLIOGRAPHYBIBLIOGRAPHY


J/J/ cross section cross section

E771/E789 : scaled to HERA-B cms energy s(J/)=352 ± 2 ± 26 nb/nucleon

E771/E789

HERA-B measurement on min. bias data ongoing

HERA–B Preliminary


Detector characteristics (I)Detector characteristics (I)

Large acceptance: 15-220 mrad in x (bending plane),15-160 mrad in y (vertical plane)

Target – up to 8 wires inserted into the halo of 920 GeV proton beam (C, Ti, W)

VDS – Vertex Detector System. Dilepton vertex resolutions: sz 600 m, sx,y 70 m

Dipole Magnet- field integral 2.13 Tm OTR – Outer Tracker. Honeycomb drift cells; wire pitch 5/10

mm; spatial hit resolution 350 m; Backward hemisphere in CM (negative xF)World largerst honeycomb tracker: 1000 modules, 115000 channels

ITR – Inner Tracker: MicroStrip Gas Chambers, pitch 100 m, resolution 100 m; Forward hemisphere in CM (positive xF)Not used in this analysis (stability issues)


Detector characteristics (II)Detector characteristics (II)

RICH – Ring Imaging Cherenkov Detector C4F10 radiator gas, 2 planes of PMT

4s separation: e/ p [3.4, 15] GeV/c, /K p [12,54] GeV/c ECAL – Electromagnetic CALorimeter – Sandwich sampling

calorimeter (“Shashlik”); Pb and W as converter; 3 regions MUON detector – 4 tracking stations; Gas pixel chambers,

Proportional tube chambers, some with segmented cathodes DAQ system – High bandwidth, high trigger and logging

rates TRIGGER.

- Pretriggers on ECAL & MUON seeds- FLT hardware based on ITR/OTR- SLT software trigger; Tracking+Vertexing; linux farm with 240

nodes

Event reconstruction; on-line, linux farm with 200 nodes


MUON AND ELECTRON CHANNEL: MUON AND ELECTRON CHANNEL: RELATIVE X-SECTION RESULTSRELATIVE X-SECTION RESULTS

Channel ee

Target C Ti W C Ti W

Atomic weight

12 47.87 183.84 12 47.87 183.84

np91850±3

008080±1

0045380±2

0067100±7

004800±20

032400±6

00

nbb 27.8±6.3 3.0±2.1 15.5±4.5 17.8+5.8-5.2 0.9±1.0 18.4+6.2

-5.5

<εRεΔz> 0.390(4)0.389(1

1)0.396(5) 0.359(7)

0.416(21)

0.394(13)

0.96 0.96

Br(bb→J/ΨX)

2.32±0.20

RΔσA(x10-2) 3.32±0.7

84.2±2.9 3.8±1.2 3.3±1.0 1.9±2.3 6.4±2.1

RΔσ(x10-2) 3.01±0.57 3.60±0.79


b production model b production model systematicssystematics

Changing PDFs from MRST to CTEQb quark mass from 4.5 to 5.0 GeV/c2

QCD renormalization scale from 0.5 o to 2 o

Fragmentation functionsPeterson form with from 0.002 to 0.008Kartvelishvili form with from 12.4 to 15.0

<kT2> from 0.125 to 2.0 GeV2

Fraction of b-baryons produced in the b-hadronization process from 0 to 12%

±1.5% ±1% ±2% ±3%

±1% ±2%

Default model: MRST PDF, Peterson FF =0.006 22222 GeV/c 0.5kpmGeV/c 4.75m TTbb 0

Total: ±5%

Studied variations: Sys cont. to s(bb )


J/J/ from b decays kinematics from b decays kinematics

92% of J/ are produced in our xF range


: Theory (preliminary): Theory (preliminary)

Theoretical prediction: NLO + (NNLO+NNNLL)Uncertainties:

b massRenormalization scale

Compatible with Modified Craigie parameterisation

HERA-B preliminary

august 25 2005hernan wahlberg, hadron051/26 open and hidden beauty in 920 gev proton-nucleus...

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