CMS / ATLAS production: quarkonia, cross section, correlations

Valery P. AndreevUniversity of California, Los Angeles

on behalf of the CMS and ATLAS Collaborations

12th International conference on B-physics at Hadron Machines

BEAUTY09, Heidelberg, Germany

7-11 September 2009

Valery Andreev, UCLA

Outline• Introduction• LHC: schedule, ATLAS/CMS detectors• onia production at LHC

– triggers– cross sections– polarization

• b production at LHC– b tagging– cross sections– high luminosity run (PT reach)

– correlations• conclusions

2BEAUTY09, 7-11 Sept. 2009

Valery Andreev, UCLA

Heavy Flavor study prospects in ATLAS and CMS vs luminosity

• Cross sections for beauty, charm, onia

Prompt and indirect J/Ψ, exclusive B decays• Onia production study

– polarisation, correlations, Υ• bb correlations• Life time of B hadrons• high PT b production cross section

• Bs oscillations

• CP violation• FCNC rare decays (B μμK, Bs μμ, …)

BEAUTY09, 7-11 Sept. 2009 3

−

Ο ( 10 pb-1)

Ο ( 100 pb-1)

Ο ( 1 fb-1)

Ο ( 10 fb-1)

Valery Andreev, UCLABEAUTY09, 7-11 Sept. 2009 4

Heavy Flavour production

• b production at hadron colliders– Huge cross section

– in other SM processes (top, Z, …)– Challenge for perturbative QCD

– Tevatron measurements are on top of NLO QCD calculations

– New physics searches: • b jets as a signal feature (SM Higgs,

SUSY decay chains, …)• b jets as a background

• onia production at hadron colliders– prompt quarkonia production not yet

understood– Color Singlet Model, Color Octet

Mechanism, NRQCD, ...– polarisation measurements challenging

theory as well

A.Grelli, EPS09

Valery Andreev, UCLABEAUTY09, 7-11 Sept. 2009 5

The CMS detector

Onion structure:• Tracker• Calorimeters• Muon system

Precise e, , , jets, ET

Efficient b tagging, detection

General-purpose detector

Valery Andreev, UCLABEAUTY09, 7-11 Sept. 2009 6

Muon detector

The ATLAS detector

TRT and Si tracker

Tile CALLAr CAL

Toroids2T solenoid

General-purpose detector

Valery Andreev, UCLA

LHC schedule 2009-2010

BEAUTY09, 7-11 Sept. 2009 7

http://lhc-commissioning.web.cern.ch/lhc-commissioning/luminosity/09-10-lumi-estimate.htm

~30÷45 pb-1 @ 7 TeV

~270 pb-1 @ 8-10 TeV

Valery Andreev, UCLA

Quarkonia production measurement at LHC (CMS)

• low luminosity (start-up) conditions– Lowest possible trigger thresholds, if any

• Double-muon trigger with PT > 3 GeV/c, |η| < 2.4

• Single muon trigger with threshold PT > 3,5,9 GeV/c – depends on lumi– open-muon trigger at start-up

• Displaced dimuon vertex trigger

– Take advantage of already aligned by cosmics tracker• close to ~ 100 pb-1 collision data alignment scenario

• Expectation for 10 pb-1

– 250k J/Ψ– 60k b J/Ψ X – 60k Υ

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Helpful in detector calibration and trigger/tracker/muon chambers commissioning

Valery Andreev, UCLA

Quarkonia production measurement at LHC (ATLAS)

• Trigger (dimuon)– Topological dimuon trigger – μ6μ4 μ1: PT > 6 GeV/c μ2: PT > 4 GeV/c

• μ4μ4 at start-up

OR– single muon trigger PT > 6 GeV/c

(μ4 at start-up)

– dimuon trigger seeded by single muon, extended region of interest• off-line: mass and vertex cuts

BEAUTY09, 7-11 Sept. 2009 9

μ1μ2

μ1

no vtx and cτ cut PromptJ/ψ and ϒ production

J/ψ with CMS ATLAS

ATLAS

trigger 2μ3 μ6μ4mass res.(MeV) 30 54yield/10pb-1 250k 150k

ATLAS, CERN-OPEN-2008-020

Valery Andreev, UCLA

J/ψ production study (CMS)

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PAS BPH-07-002

Inclusive J/ψ cross section:1-D fit to mass spectra

Prompt vs non-prompt (BJ/ψ X):2-D fit to mass spectra and pseudo-proper decay length

3 pb-1 3 pb-1

• Systematics dominatedalready at start-up Systematics at ~15% level

• Competitive with Tevatron starting with the first picobarns

Valery Andreev, UCLA

J/ψ and ϒ production (ATLAS)

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no vtx and cτ cut • 10 pb-1 estimate• prompt fraction selected by vertexing, cut on pseudo-proper time

Polarisation as discriminant betweenmodels

€

t =Lxy • MJ / Ψ

pTJ / Ψ • c

Valery Andreev, UCLA

Quarkonia polarization analysis

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ATLAS

CMS

Tevatron: no model to describe cross section and polarization at the same time

efficiency depends on polarisation

α parameter:+1 – transverse polarization- 1 – longitudinal

0 – unpolarized

Valery Andreev, UCLABEAUTY09, 7-11 Sept. 2009 13

B-production / QCD aspects• present status of the production phenomenology at hadron colliders

– The shape of transverse momentum and angular distributions as well as the azimuthal angular correlations in a reasonable agreement with perturbative QCD

– The observed cross-sections are larger than QCD predictions– The agreement between experiment and theory has improved due to the

evolution of latter mostly a consequence of improved experimental inputs• More precise parton density function, up-to-date s• Improvement on fragmentation effects estimate

– The agreement is not complete, to improve the phenomenologicaldescription requires new experimental input (LHC)Review on R=σb/σNLO, F.Happaher, P.Giromini,F.Ptohos PRD 73, 014026 (2006)

• experiment is systematically above NLO QCD prediction

Valery Andreev, UCLABEAUTY09, 7-11 Sept. 2009 14

B acceptance• ATLAS/CMS

– || < 2.5/2.4 • Tracker/muon detector

acceptance

– high-Pt muon trigger– b-tagged jet trigger

• LHCb – Forward spectrometer

• 1.9 < < 4.9

– much softer pt triggers

There is an overlapCMS study: much higher Pt can be reached

Valery Andreev, UCLA

B tagging

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CMS PAS-BTV-07-003 (2008)

• most performing: Combined Secondary Vertex algorithm (high luminosity run)

• different misalignment scenarios studied

• SoftMuon algorithm:• efficiency < 20 %

(B branching ratio)• robust against

misalignment

Valery Andreev, UCLABEAUTY09, 7-11 Sept. 2009 16

CMS Analysis: Inclusive b production

• B production total cross section • Differential cross sections d/dpt’ d/d

– Selection • b-tagged jet• semileptonic b-decays into muons

– Luminosity: 10 fb-1

CMS Note 2006/120, V.P. Andreev, D.B. Cline, S. Otwinowski

• The most energetic b tagged jet as the reconstructed B-particle candidate• the rate of b jets is a direct measurement of

the b production with only small fragmentation systematics

Valery Andreev, UCLABEAUTY09, 7-11 Sept. 2009 17

Event selectionTrigger

Level-1: High Level Trigger: “single m”, “muon + b-jet”,

pt>14 GeV/c, || < 2.1 Pt >19GeV/c, Et

jet>50GeV, || < 2.4

e = 18 % e = 60 %

Off-line selection

• B-tagged jet: Et > 50 GeV, || < 2.4

e = 65 % (barrel), 55 % (endcap)

• Muon associated with B-tagged jet

e = 75 %

Valery Andreev, UCLABEAUTY09, 7-11 Sept. 2009 18

B-jet resolution/B-tag efficiency

= 12.9 % = 5.7 %

Pt > 170 GeV/cB tag:

inclusive secondary vertex in jets

Valery Andreev, UCLABEAUTY09, 7-11 Sept. 2009 19

Fit results

Muon Pt w.r.t. the closest B jet

QCD events MC: 230 < Pt < 300 GeV/c

Nb =5250 (56 %Nc = 2388 (26%Nudsg= 1740(18% --------- 9378 events

Fit:

Nb =5222 501 Nc = 2050 728 Nudsg =1778 341 --------- 9050 events

bcudsg

Valery Andreev, UCLABEAUTY09, 7-11 Sept. 2009 20

b-quark Pt reach

We can reach 1.5 TeV as the highest measured B hadron Pt

B hadron – Pt > 50

GeV/c– | | < 2.4

statistical

systematic

Valery Andreev, UCLABEAUTY09, 7-11 Sept. 2009 21

B production at LHC, PT reach

Extended Pt reach

CMS analysis summary• ~16 M b events to be selected with 10 fb-1

• b purity in a range from 70 % to 55 %

• up to 1.5 TeV B-hadron Pt reach

Valery Andreev, UCLA

Exclusive B production

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CMS PAS-BPH-09-001 (2009)

B+ J/ψ K+

B0 J/ψ K*0

10 TeV

Differential cross sectionscan be measured with statistical precision betterthan 10 % for 10 pb-1

luminosity (early data)

Valery Andreev, UCLABEAUTY09, 7-11 Sept. 2009 23

B production mechanisms at LHC

Pair creation (LO) : ~50 b

hep-ph/0003142

bb = 465 b ( ~ 500 b )

Gluon splitting (NLO) :

~190 b

Flavor excitation (NLO) : ~220 b

• Both, ATLAS and CMS, will measure bb-correlations• bb as discriminating variable

• B J/ X + B • bb = φJ/Ψ - φμ

PYTHIA MC prediction @ LHC

• b-jet + B • bb = φb-jet - φμ

• b-jet + b-jet• bb = φb-jet – φb-jet

Valery Andreev, UCLA

bb correlations

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_

B J/ X + B CMS PAS-BPH-08-004 (2009)

• bb fraction extracted by simultaneous 3D unbinned maximum LH to

J/ψ invariant mass, J/ψ transverse flight length, μ impact parameter• Expected total uncertainty between 15 and 25 % for 50 pb-1

Valery Andreev, UCLABEAUTY09, 7-11 Sept. 2009 25

Conclusions• data on b production and quarkonium need to be yet

reconciled with theory• ATLAS and CMS have an intense program for the QCD test

in Heavy Flavor production at LHC energies• correlations and polarization measurements are foreseen to

investigate in detail production mechanisms

• HF measurements important for New Physics search

Eagerly looking forward to the first LHC collision data

this year !