Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://nuclphys.sinp.msu.ru/conf/epp10/Polyakov.pdf Äàòà èçìåíåíèÿ: Sat Sep 7 17:56:06 2013 Äàòà èíäåêñèðîâàíèÿ: Fri Feb 28 02:38:20 2014 Êîäèðîâêà:

B decays to Charmonium at LHCb

Ivan Polyakov ITEP
on behalf of the LHCb collaboration

16th Lomonosov conference, 27 August 2013


Outline



LHCb detector + B selection B0J/K*0 angular analysis B0(s) decays to higher charmonium states ((2S), c) and neutrals X(3872) quantum numbers Bc+ decays Summary











Polyakov Ivan, 16th Lomonosov conference, 27 August

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LHCb detector
Features relevant for BJ/X


High efficiency single and di-muon trigger Good time resolution to select B candidates Good muon identification Good K/ separation by RICH detectors







See talk by Olaf Steinkamp

Polyakov Ivan, 16th Lomonosov conference, 27 August

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Selection


Trigger on detached Good quality tracks , K, identification (Muon & RICH) Vertex quality PV and SV separation (c > x) p IP Primary vertex (PV) Secondary vertex (SV)
1cm

-



K+ +





B p

J/





Daugther particles not from PV (cut on IP > 2, pT > x) B-candidate from the PV Decay structure consistent






Efficiencies and background:
Efficiencies from simulation (when possible from data ­ for PID, trigger) use sPlot technique to subtract backgound
4



Polyakov Ivan, 16th Lomonosov conference, 27 August


Angular analysis of B J/K
0


*0

The decay (SVV) can be decomposed as


P-wave: A0(longitudial), A||(transverse-parallel), A(transverse-perpendicular) S-wave: As(non-resonant K) Strong phases: 0=0 ,|| , and Parity: even(A0, A||), odd(A, As)
s









Probe BSM contributions, which are approximately equal to those in BsJ/ (golden mode for CPV in Bs) See talk by Olaf Steinkamp To measure the amplitudes the angular analysis is performed

L = 1.0 fb-1 N ~ 77 000



Polyakov Ivan, 16th Lomonosov conference, 27 August

arXiv: 1307.2782

5


Angular analysis of B J/K
0
P-even P-even P-odd P-odd S-wave

*0

P-even P-odd S-wave P-odd S-wave P-even

Dominant systematic unc. - acceptance - contribution from other resonances in K

A2= 0.227±0.004 ±0.011 , A 2=0.201 ±0.004 ±0.008 , [ rad ] =-2.94 ±0.02 ±0.03 , [ rad ]= 2.94 ±0.02± 0.02

Consistent with previous measurements and SM predictions

Polyakov Ivan, 16th Lomonosov conference, 27 August

arXiv: 1307.2782

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B decays to charmonium



Crucial role in CP violation studies [see talk of Olaf Steinkamp] & precise measurement of neutral B mixing parameters


new possible channels for CPV studies in B

0 s



Sensitive labarotary for electro-weak transition studies Direct probe of charmonium properties Study light quarks





J/, (2S), d, s

c

K*0, ,0, ('), 0,...

Polyakov Ivan, 16th Lomonosov conference, 27 August

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Observation of B (2S)
0 s


B0sJ/ has been previously seen by Belle [PRL 108 (2012) 181808] and LHCb [NPB 867 (2013) 547]

L ~ 1.0 fb-1 N = 76 ± 12 S = 6.2
first observation !

B0s(2S)

L ~ 1.0 fb-1 N = 863 ± 52

B0sJ/

normalization channel

B0J/

Fixed to PDG



Similar study for B0(2S) and B0s(2S) Explore intermediate resonance structure with sPlot Dominant systematics: efficiencies from simulation

+ -



BR ( B s ( 2S) ) BR ( B J / )
th

0

0 s

=0.83 ±0.14 ( stat )± 0.12 ( syst ) ±0.02 ( BR

)
Nucl. Phys. B871 (2013) 403

Polyakov Ivan, 16 Lomonosov conference, 27 August

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Study of B


0 (s)



c1,2

K*0( )

In factorization approach B respect to Bc1K()

c 0,2

K() decay modes are expected to be suppressed with



But the measured BR(B0c0K*0) = (1.7±0.3±0.2)x10-4 [BaBar, PR D78 (2008) 0911001] is compatible with BR(B0c1K*0) = (2.5±0.2±0.2)x10-4 [BaBar, PRL 102 (2009) 132001] and BR(B0c1K*0) = (1.73+0..15 +0..34 )x10-4 [Belle, PR D78 (2008) 072004] - 0 12 - 0 22 While BR(B0c2K*0) = (6.6±1.8±0.5)x10-5 [BaBar, PRL 102 (2009) 132001] can still be explained in factorization approach The B0sc have not been previously observed





Polyakov Ivan, 16th Lomonosov conference, 27 August

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Study of B
0
L ~ 1 .0 fb
-1

c1,2

K

*0
B0c1K*0 N = 566 ± 52

B0c1K* B0c2K*
0

0

shift in agreement with MC

L ~ 1 .0 fb

-1

Background subtraction (sPlot) B0c1K*
0

B0c2K*0 N = 66 ± 19

B0c2K

*0

shift in agreement with MC



Constraint J/ mass to c1,2 to resolve two peaks mass shift in agreement with simulation
BR ( B 0 c1 K 0)
0 0

Dominant systematic: - signal determination - photon reconstruction
-2

BR ( B J / K ) BR ( B0 c2 K 0) =( 17.1±5.0 ( stat ) ±1.7 ( syst )±1.1 ( BR BR ( B0 c1 K 0)
Polyakov Ivan, 16th Lomonosov conference, 27 August

=( 19.8 ±1.1 ( stat )±1.2 ( syst )±0.9 ( BR

c J /

) )â10

c J /

) )â 10

-2

Compatible with previous measurements, but more precise
Nucl. Phys. B874 (2013) 663 10


Study of B0s

c1,

2
B0sc2 N = 66 ± 19

L ~ 1 .0 fb

-1

S>9
first observation !

Background subtraction (sPlot)



Measure branching ratio relatively to B0sJ/

Dominant systematic: - signal determination - photon reconstruction

BR ( B 0 c1 ) s BR ( B J / )
0 s

=( 18.9±1.8 ( stat )±1.3 ( syst )± 0.8 ( BR

c J /

)) â10

-2

Nucl. Phys. B874 (2013) 663 Polyakov Ivan, 16th Lomonosov conference, 27 August 11


X(3872) quantum numbers

X(3872) was discovered by Belle in 2003 [PRL 91 (2003) 262001], but it's nature still unclear


C-parity = +1 since X(3872)J/ is observed CDF excluded all J
PC



combinations except 1++ and 2-+ [PRL 98 (2007) 132002]



BaBar favoured 2-+ (68% CL) by studying X(3872)J/0, but not ruled out 1++ (7% CL) [PRD 82 (2010) 011101] Belle couldn't distinguish 1++ and 2-+ by analysing 1D distributions [PRD 84 (2011) 052004]



Determination of quantum numbers is crucial for the interpretation of the state


1++: molecular, tetraquark, c(23P1)? 2-+: c(11D2)?



Polyakov Ivan, 16th Lomonosov conference, 27 August

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X(3872) quantum numbers


5-D angular analysis of B+X(3872)K+, X(3872)J/+-



Angular distributions carry information about J

PC

L ~ 1 .0 fb

-1

B+(2S)K+, N = 5642±76 B+X(3872)K+, N = 313±26

Polyakov Ivan, 16th Lomonosov conference, 27 August

Phys. Rev. Let. 110, 222001 (2013)

13


X(3872) quantum numbers


Angular correlations magnify differences between spin hypothesis:

Likelihood-ratio test to discriminate between to hypothesis t = -2ln[L(2-+)/L(1++)] Compare with simulated statistics



8.4

Result: 2-+ is rejected with 8.4, with p-value for 1++ of 34%
Phys. Rev. Let. 110, 222001 (2013) 14

Polyakov Ivan, 16th Lomonosov conference, 27 August


Bc decays


The Bc meson, composed of two heavy quarks (bc), is a unique, being the only weak decaying heavy quarkonium system Prior to LHCb only the Bc+J/+ and Bc+J/+ decays were observed





At LHCb f(bBc+) ~ 1/1000 LHCb has already observed new decay mode: Bc+J/+-+ [PRL 108 (2012) 251802] Four more new decay modes in this summer see next





Polyakov Ivan, 16th Lomonosov conference, 27 August

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Bc+(2S)


+

Test different theoretical models for B decays

+ c



Analysis strategy: - multivariate selection (BDT) to supress background - Bc+J/+ as normalization channel

Bc+J/+ normalization channel

L ~ 1.0 fb-1 N = 595 ± 29



Dominant syst: - understanding of the BDT selection - background shape
+ c + + c +

L ~ 1.0 fb-1 N = 20 ± 5 S = 5.2

first observation !

BR ( B ( 2S ) ) / BR ( B J / ) = 0.250 ±0.068 ( stat )±0.014 ( syst )±0.006 ( BR )


Bc+(2S)

+

The result favours relativistic quark model prediction with respect to the others
Phys. Rev. D 87, 071103(R) (2013) 16

Polyakov Ivan, 16th Lomonosov conference, 27 August


Bc+J/K+


pion-like

The branching fraction relative to Bc+J/+ is measured



Naive expectation:



Theoretical predictions lie within 0.054 ­ 0.088 range test hadronization model Analysis strategy: - Multivariate selection (BDT) - bins of discriminating K­ identification variable
L ~ 1.0 fb-1 N = 46 ± 14 S = 5.0
first observation !



kaon-like

BR ( Bc J / K ) BR ( Bc J / )
+ +

+

+

= 0.069± 0.019± 0.005

Dominant systematic: - understanding of the BDT selection
arXiv:1306.6723 17

Polyakov Ivan, 16th Lomonosov conference, 27 August


Bc+J/Ds+


(*)
can contribute in contrast to decays of other B mesons

The branching fraction relative to Bc+J/+ is measured Three leading contributions Test assumption that spectator one dominates & factorization holds Low energy release allows precision mass measurement
N(Ds+) = 28.9 ± 5.6 first observations !







S>9 L ~ 3 fb

BR ( Bc J / D s ) = 2.90± 0.57 ( stat )±0.24 ( syst ) + + BR ( Bc J / ) + + BR ( Bc J / D s ) = 2.37±0.56 ( stat )±0.10 ( syst ) + + BR ( Bc J / D s )


+

+

-1

Compatible with naive expectations from BD*Ds(*)+(+) decays
mB = 6276.28±1.44 ( stat )±0.36 ( syst ) MeV / c
+ c

2

N(Ds*+)/N(Ds+) = 2.37 ± 0.56


In agreement with PDG (2013 update): m(Bc+) = 6274.5 ± 1.8 MeV/c2
Phys. Rev. D 87, 112012 (2013) 18

Polyakov Ivan, 16th Lomonosov conference, 27 August


Conclusion
LHCb shows excellent performance in measuring B decays to charmonia


Provide input for measurements of CPV and mixing in B mesons Explore charmonium properties





Serie of new decays observed (B0s(2S), B0sc1, Bc+...) X(3872) quantum numbers determined to be 1
(Bc+J/K+, Bc+J/D
(*)+ s



++



Study of properties and observe new decays of the Bc+ meson
)



Plus many other analysis, for instance


Precision measurement of b lifetime [arXiv:1306.6723] First upper limits on BR(B0sJ/pp) and BR(B+J/pp+) [arXiv: 1306.4489] ...





Thank you!
Polyakov Ivan, 16th Lomonosov conference, 27 August 19


Backup

Polyakov Ivan, 16th Lomonosov conference, 27 August

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b lifetime


According to Hevay Quark Expansion model (b)/(B) 1 with difference only a few persent expected Average experimental give 0.798 ± 0.052 [arXiv:hep-ph/0304132] 0.786 ± 0.034 [arXiv:hep-ph/0310241, arXiv:hep
-ph/0203089]





Precision measurement is necessary



Strategy:


Use similar decay modes bJ/pK- and B J/+K- systematic uncertainty cancels in the ratio BDT Sideband to subtract background
L ~ 1.0 fb-1 N ~ 16 000
first observation!
relection from B





combinatorial bkg

Sidebands
Polyakov Ivan, 16th Lomonosov conference, 27 August arXiv:1306.6723 21


b lifetime


Use whole pK mass region Decay time acceptance from simulation weighted to match pK(K) mass distribution Determine (1520)





1 1 B = - B

from ratio of yields



Dominant uncertainty: ­ decay time fit range ­ acceptance slope



In agreement with HQE expectation of (b)/(B) = 1 Consistent with, but more precise than, current world average: (b) = 1.429 ± 0.024 ps



Polyakov Ivan, 16th Lomonosov conference, 27 August

arXiv:1306.6723

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B decays to charmonia and dibaryons



The study of such decays has not been extensively explored mainly due to the suppressed branching fractions of typically O(<10-5) Dibaryon production in B meson decays has been studied in decays B+K+pp or B0D0pp Branching fraction is ~10% that of the corresponding decay with pp replaced by +In contrast







BR ( B 0 J / + - ) = ( 4.6±0.9 )â10
BR ( B J / p p ) < 8.3 â10
0 -7

-5

~ 50 times difference

Polyakov Ivan, 16th Lomonosov conference, 27 August

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B0(s)J/pp and B+J/pp

+

No significant signals are seen

BR ( B J / p p ) <5.2 ( 6.0 )â10 BR ( B 0 J / p p ) < 4.8 ( 5.3 ) â10-6 s + + -7 BR ( B J / p p ) <5.0 ( 6.1 )â10

0

-7

@ 90 ( 95 ) CL @ 90 ( 95 ) CL @ 90 ( 95 ) CL

first limits!

Polyakov Ivan, 16th Lomonosov conference, 27 August

arXiv: 1306.4489

24


Observation of B

0 (s)

(2S)+-

B (2S)
0 +

-

B (2S)
0 s +

-

B0J/+B0sJ/+first observation!

B0(2S)K+-

B0J/K+-

BR ( B 0 ( 2S ) + - ) =0.56 ±0.07 ( stat ) ±0.05 ( syst )±0.01 ( BR 0 +- BR ( B J / ) BR ( B0 ( 2S ) + - ) s =0.34 ±0.04 ( stat )±0.03 ( syst )± 0.01 ( BR 0 +- BR ( Bs J / )
Polyakov Ivan, 16th Lomonosov conference, 27 August



+

-

) )

+

-

Nucl. Phys. B871 (2013) 403 25