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The XXth International Workshop

High Energy Physics and Quantum Field Theory
September 24 - October 1, 2011, Sochi, Russia

LHCb; inclusive bb-quarkonium production
Konstantin Belous on behalf of LHCb Collaboration
Institute for High Energy Physics (IHEP), Protvino Outlook: Ç Reminder: LHCb detector and status Ç (1S) production Ç Sources of (1S) and b(1P) observation Ç Quarkonia at LHCb Ç Conclusion


LHCb detector
Forward single arm spectrometer covering 15?300 mrad (2 < < 4.9)

Ç charged tracks p/p = 0.35%?0.55% mass resolution 13 MeV/c2 on J/ÅÅ and 50 MeV/c2 on ÅÅ Ç vertexing: PV resolution 16 Åm in X,Y and 76 Åm in Z proper time resolution 30?50 fs Ç Muon ID: (ÅÅ) = 97%, mis-ID rate (Å) = 1?3%
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Status
Ç LHCb is in very good shape: - 37 pb-1 at s = 7 TeV recorded in 2010 - 800 pb-1 already in 2011 - Expect 1 fb-1 at the end of the year Most of the quarkonia analyses use data of 2010

Ç

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Motivation
Ç Ç Ç Many quarkonia states is discovered Nevertheless the production mechanism in pp-collision is not fully understood Large cross-section is expected at LHC High rate makes quarkonia central player for detector and software calibration Several theory models of production mechanism is around - Started with Color singlet (CSM)
under-predict, no polarization prediction

Ç

- Extended to Color octet (COM) mechanisms, (NRQCD)
better agreement for cross-sections; predicts transverse polarization, not confirmed by experiments

- NLO CSM better describes cross-section and allow longitudinal polarization - Other models (Color evaporation (CEM), kt factorization, soft color interaction) Ç New data from LHC experiments will help to resolve this issue
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(1S) Å+Å-
(1S) production cross-section LHCb-CONF-2011-016 Analysis performed on 2010 data


(1S); Trigger and Event Selection
Trigger lines important for Å+Å- events
L0 Trigger HLT1 Trigger Single Muon Di-Muon Single Muon Di-Muon HLT2 Trigger Di-Muon pT > 1.4 GeV/c p
T1

> 0.56 GeV/c, p

T2

> 0.48 GeV/c

Confirm L0 Single Muon and pT > 1.8 GeV/c (Prescaled) Confirm L0 Di-Muon and m(Å+Å-)>2.5 GeV/c2 m(Å+Å-)>2.9 GeV/c2 or cuts on vertex and track quality

Å-tracks: Ç well reconstructed tracks identified as muons in muon detector, Ç pT > 1 GeV/c, ÇTrack fit quality
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Reconstructed : Ç vertex fit quality Prob(2) > 0.5% Ç mass window: 8 - 12 GeV/c2

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Di-muon invariant mass spectra

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Cross-section measurement strategy
d ( pp ) Br ( Å + Å dpT dy
Ç Ç Ç Ç
-

)

=

N

fit

(

pT , y,

tot

)



Ldt pT y

Nfit - number of candidates in the mass peak in each pT, y bin, obtained from the fit and corrected for acceptance and efficiency tot - total efficiency (including acceptance) pT, y - bins of pT and y



Ldt - integrated luminosity

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Number of candidates
Ç Parameters and n of Crystal Ball functions are fixed: = 2, n = 1 3 Crystal Balls(CB) + exponential for background

Ç The same function is used for individual bin fits

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Number of candidates
Ç Numbers of (1S) candidates are extracted from Crystal Ball (CB) part of the fit with 3CB+exponential. Only (1S) considered: - Width and masses of (2S) and (3S) are fixed. Rapidity interval 2.0 < y < 2.5

0
1
2
Ç

6
7
8
Ç

9
10
11
12
13
14
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Number of (1S) candidates

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Efficiency
The efficiency
tot

has been subdivided into three pieces:




tot

=N =



(

accepted, reconstructed, triggered ) N
rec

(

generated ) =

acc



trg

=

N ( accepted ) N ( reconstructed ) N ( triggered ) = N ( generated ) N ( accepted ) N ( reconstructed

)

For each pT,y range the following subsequent sub-samples and numbers of (1S) in them are defined: Ç N(generated) - Total number of (1S) generated Ç N(accepted) - Number of generated inside LHCb acceptance
(10-400 mrad)

Ç Ç

N(reconstructed) - Number of accepted, detected and reconstructed N(triggered) - Number of triggered
K.Belous, QFTHEP'2011 12

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Acceptance

acc

N (gen. with Å + Å - in 0 < pT < 15 GeV/c, 2 < y < 4.5, 10 < < 400 mrad) = N (generated with Å + Å - in 0 < pT < 15 GeV/c, 2 < y < 4.5)

pT of (1S) (GeV/c)

y of (1S)
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Reconstruction efficiency

rec

N detected and reconstructed in pT ,y range = N generated in angular acceptance in pT ,y range

pT of (1S) (GeV/c)

y of (1S)
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Trigger efficiency

trg

N detected, reconstructed, triggered in range = N detected, reconstructed in range
Calculated in data for J/ events as a function of (pTÅ1+ pTÅ2) and y Systematic uncertainty is estimated using J/ and (1S) Monte Carlo
y of (1S)

Ç

Ç

pT of (1S) (GeV/c)

pT of (1S) (GeV/c)

y of (1S)
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Systematic uncertainties
Source luminosity
trg

Method luminosity for 2010 data difference MC - MC truth
acc rec

Value 10%
(the same for each bin)

calculation

2-67%

(bin-by bin; big for some bins with low statistics) (bin-by-bin) (bin-by-bin)

polarization on polarization on

extreme polarization scenario 0-33% extreme polarization scenario 0-21% different function pT spectrum distribution difference data - MC difference data - MC difference data - MC tag and prob
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choice of fit function unknown pT spectrum (track quality) (track finding) vertexing Muon ID
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1% 1% 2% 0.5% per track 4% per track 1% 1.1%
16

GEC (Global Event Cuts) statistical uncertainty of data


Effect of polarization on acceptance
y()

=0

pT() (GeV/c)

= -1

pT() (GeV/c)

= +1

pT() (GeV/c)

= -1 = +1
pT() (GeV/c)
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- full longitudinal polarization - full transverse polarization - no polarization
17

y()
K.Belous, QFTHEP'2011

=0


Effect of polarization on

rec

pT() (GeV/c)

y()

= -1 = +1 =0
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- full longitudinal polarization - full transverse polarization - no polarization
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(1S) cross-section

108.3 Á 0.7(stat.)
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+30.9 -25.8

(syst.) nb, 0 < pT ( ) < 15 GeV/c, 2 < y < 4.5
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Comparison with CMS
CMS publication:
[Phys. Rev. D83 (2011) 112004;

arXiv: hep-ex/1012.5545v1]

Ç

Ç

CSM measurement as a function of pT is higher, but it should be noted that CMS measure cross-section for |y|<2, while LHCb for 2.0
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Comparison with theory
NLO CSM P.Artoisenet, PoS ICHEP 2010 (2010) 192. NLO & NNLO CSM J.-P.Lansberg, Eur. Phys. J. C 61 (2009) 693

NLO NRQCD Y.Q.Ma, K.Wang and K.T.Chao, Phys. Rev.Lett. 106 (2011) 042002.

NLO CEM A.D.Frawley, T.Ullrich and R.Vogt, Phys. Rep. 462 (2008) 125.

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Sources of (1S)
Ç Feed down from higher bottomonium states ((2S), (3S), b, etc.) need to be understood in order to interpret the measurement of (1S) production and study its polarization. CDF experiment analyzed the sources of (1S) production based on statistics of RUN I period (90 pb-1, s=1.8 TeV, 1994-1995 years). PRL 84 (2000) 2094, hep-ex/9910025. For: Source Fraction in % - pT() > 8 GeV/c calculated Direct 50.9Á8.2Á9.0 - | ()| < 0.7 35.3Á9 events b(1P) 27.1Á6.9Á4.4 they obtain...
28.5Á12 events b(2P) (2S) (3S) 10.5Á4.4Á1.4 10.7+7.7-4.8 0.8+0.6-0.4
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Ç

from ((2S)) and Br((2S)(1S) +- from ((3S)) and Br((3S)(1S) +-
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b selection criteria:
(1S) mass band Polar angle of Å in rest frame
+

b(1P) observation
9.36?9.56 GeV/c |cos Å| < 0.7
* 2

dN dx

1 = A1 e 2 + A2 ( x - x0

-

(

x -M 2
2

)

2

+
3

pT of photon Polar angle of in rest frame pT of b candidate
b

pT() > 700 MeV/c cos* > 0 pT(b) > 7 GeV/c

)



( e

- a1 x + a 2 x 2 + a 3 x

)

Ç Ç Ç Ç

A clear signal for b(1P) production is seen. No hint for b(2P) signal (M800 MeV/c2). Cannot do a separation of the states (b0(1P), b1(1P), b2(1P)) yet. Gaussian (for signal) + smooth background function is used for fitting to obtain the number of signal candidates.
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Quarkonia at LHCb
Ç Ç Prompt quarkonia production probe NRQCD and help to understand colorsinglet and color-octet contributions. LHCb has already a lot of interesting results:
LHCb-CONF-2011-016

(1S) production cross-section J/ production cross-section Double J/ production

Eur.Phys.J C71 (2011) 1645 LHCb-CONF-2011-009 arXiv: hep-ph/1109.0963v1 LHCb-CONF-2011-026 LHCb-CONF-2011-043 LHCb-CONF-2011-020

(2S) production cross-section Inclusive X(3872) production c2/c1 cross-sections ratio

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J/ production cross-section
Performed on first data 5.2 pb with J/ÅÅ
-1

Eur. Phys. J. C71 (2011) 1645

Ç Measured in bins of - rapidity 2.0 the last error due to unknown polarization
-2.20

Ç (from b)=1.14Á0.01Á0.16 Åb

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J/ production cross-section
NLO NRQCD K.T.Chao et al.
[Phys.Rev.Lett. 106 (2011) 042002, arXiv: hep-ph/1009.3655]

NLO CSM NNLO CSM J.-P. Lansberg
[Eur.Phys.J. C61 (2009) 693, arXiv: hep-ph/0811.4005]

NLO CEM R.Vogt
[Phys.Rep. 462 (2008) 125, arXiv: nucl-ex/0806.1013]

FONLL (fron b) M.Cacciari, M.Greco, P.Nason,
[J. High Energy Phys. 9805 (1998) 007 hep-ph/9803400]

M.Cacciari, S.Frixione, P.Nason,
[J. High Energy Phys. 0103 (2001) 006 hep-ph/0102134]

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Double J/ production
LHCb-CONF-2011-009 arXiv: hep-ph/1109.0963v1 Analysis performed on 2010 data Ç Ç Ç Ç Ç 4 muons from the same vertex Fit M(Å+Å-)1 in bins of M(Å+Å-)2 140Á18 double J/ (J/ J/) = 5.6Á1.1Á1.2 nb QCD calculations [A.V.Berezhnoy, et al., arXiv: hep-ph/1101.5881v1], which does not includes non-direct J/ J/, predicts: (ppJ/ J/ X) = 4.15?4.34 nb

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(2S) production
LHCb-CONF-2011-026 Analysis performed on 2010 data
Ç Theoretically interesting state. No feed down contribution. Ç Differential cross-sections measured: +0.25 (2S) Å+Å- (0
M(Å+Å-) (MeV/c2)

M(J/+-) (MeV/c2)
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X(3872) production and mass
LHCb-CONF-2011-021 LHCb-CONF-2011-043 Analysis performed on 2010 data

L = 34.7 pb
Ç

-1

N

signal

= 585 Á 74

Exotic meson discovered by Belle in 2003 in b meson decays Nature still uncertain: most popular model is molecular state with JPC = 1++ M
X(3872)

Ç Ç

= 3871.96 Á 0.46 Á 0.10 MeV/c2

X(3872) ç Br(X(3872)J/ +-) = = 4.74 Á 1.10 Á 1.01 nb

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c2/c1 cross-section ratio
LHCb-CONF-2011-020 Analysis performed on 2010 data

converted

L = 35.6 pb

-1

not converted

( c2 ) N = ( c1 ) N
Ç Ç



c2



c1



J / J /



c1



c2


c1 c2



sel sel

c1

c2

Br ( c1 J / Br ( c 2 J /

) )

converted (e+e- clusters) and not converted ( cluster) treated separately Efficiencies cancel out, lower systematic uncertainty
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Br ( c1 J / ) ( 34.4 Á 1.5 ) % = Br ( c 2 J / ) (19.5 Á 0.8 ) %

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c2/c1 cross-section ratio
Ç Ç Internal error bars: statistical error from the yield extraction External error bars: systematic uncertainty included: - decay branching fractions - stability of fit - MC statistics Shaded area (black): maximum effect of unknown polarization Shaded area - theory predictions: - (red): CSM - (blue): NLO NRQCD

Ç Ç

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Conclusion
Ç LHCb performs many analyses of quarkonium states using 2010 collected data - (1S) - J/ (separately prompt and non-prompt) - double J/ - (2S) - c2 to c1 cross-section ratio These results are useful to test theoretical models Good agreement of cross-section (J/,(2S),(1S)) measurements with NRQCD The experimental error is lower than the theoretical one LHCb collect high statistics in 2011 - more than 800 pb-1 collected do far - 1 fb-1 expected at the end of 2011 - a lot of new results expected in the future

Ç Ç Ç Ç

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