View
226
Download
5
Tags:
Embed Size (px)
Citation preview
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
BEAUTY09, 7-11 Sept. 2009 8
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)
BEAUTY09, 7-11 Sept. 2009 10
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)
BEAUTY09, 7-11 Sept. 2009 11
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
BEAUTY09, 7-11 Sept. 2009 12
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
BEAUTY09, 7-11 Sept. 2009 15
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
BEAUTY09, 7-11 Sept. 2009 22
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
BEAUTY09, 7-11 Sept. 2009 24
_
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 !