b Production Cross Section and Fragmentation Fractions at LHCb

b Production Cross Section and

Fragmentation Fractions at LHCb

• Motivation• LHCb• b-cross section

Semi-leptonic B0/+→D0Xμν J/ψ b →J/ψX

• Fragmentation fractions fs/fd Semi-leptonic B(s)

0/+→D(s)+/0Xμν

Hadronic B0s→Ds

-π+ and B0→D-

π+/K+

Niels Tuning on behalf of the LHCb collaboration

Amsterdam, 5 April 2011

Motivationb cross section:• Comparison to QCD predictions• Knowledge of b-yield to ascertain sensitivities in B-physics analyses

Fragmentation fractions, fs/fd:• Input to e.g. inclusive b cross section measurement• Needed for all Bs

0 branching ratios In particular BR(B0

s→ μ+μ-)

5 Apr 2011 b cross section and fs/fd at LHCb

Number of measured Bs0 decay modes is limited:

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+ LHCb:Γi : Bs

0→K*0K*0

Γi : Bs0→D0K*0

Γi : Bs0→Ds2 (2573)μν

Γi : Bs0→ J/ψf0 (980)

23 sep 2010 19:49:24Run 79646 Event 143858637

The LHCb Detector

5 Apr 2011 b cross section and fs/fd at LHCb 3/29

InteractionPoint

Suppress background, σ(MB)B(s)

0 →D(s)-K/π

Lifetime, B0

(s)

The LHCb DetectorB0

(s)→D(s)Xμν

5 Apr 2011

Trigger & PID:B(s)

0→ D(s)-K/π

b cross section and fs/fd at LHCb

MUON CALO RICH2 T MAGNETRICH1

VELO

PIDB(s)

0→D(s)-K/π

TT

See also Neville Harnew. Monday 10:10,LHCb detector performance

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LHC and LHCb performance

eff LHCb = 90.3%

LHC and LHCb show excellent performance

Recorded 38 pb-1

1010bb-pairs produced


b cross sectionsemi-lep (15 nb-1)

fs/fd (3 pb-1)semi-leptonic

fs/fd (35 pb-1)hadronic

b cross sectionJ/ (5 pb-1)

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b cross section: semi-leptonic

• Measure pp→bbX through b→D0Xμ-ν

D0→K-π+

• Distinguish b from prompt using impact parameter:

5 Apr 2011

Prompt D0:

D0 from b:

b cross section and fs/fd at LHCb

LHCb Collaboration, R.Aaij et al.,

Phys.Lett.B694:209-216,2010, arXiv:1009.2731

For more semi-leptonics, see : Rob Lambert. Thursday 9:25,Semileptonic decays (beauty/charm) & plans at LHCb

6/29



Phys.Lett.B694:209-216,2010, arXiv:1009.2731

D0 mass

D0 impact parameter

Large impact parameter: from b



D0→K-π+

• 2D unbinned likelihood fit to m(Kπ) and ln(IP)

For more semi-leptonics, see : Rob Lambert. Thursday 9:25,Semileptonic decays (beauty/charm) & plans at LHCb

7/29


D0 impact parameter

D0 impact parameter: (D0μ)-pairsBackground:K and μ with opposite charge



D0→K-π+

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D0→K-π+

• Result (2<η<6): σ(pp→bbX) = 75.3±5.4±13.0 μb (assuming LEP fragmentation fractions)

σ(pp→bbX) = 89.6±6.4±15.5 μb (assuming Tevatron fragmentation fractions)

• Extrapolate to full rapidity range:

LHCb Collaboration, R.Aaij et al., PLB694:209-216,2010, arXiv:1009.2731

Theoretical error(e.g. mb and μR,F)

Cacciari, Nason, Frixione, Mangano, Ridolfie.g. hep-ph/9803400

(MCFM v5.8, Campbell, Ellis)

LHCb, 15.1 nb-1

HFAG, D. Asner et al., arXiv:1010.1589

CDF, Phys.Rev.D77:072003,2008., arXiv:0801.4375

NB: translation to b→D0Xμ-νdepends on BR and fs/fd :

B0→D*-Xμ+ν → D0Yμ+ν B+ → D0Xμ+ν B0

s→Ds*-Xμ+ν → D0Yμ+ν

x

-12.2 nb-1 triggered

2.9 nb-1 microbias

combined

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• Measure pp→bbX through b→J/ψ(μ-μ+)X

LHCb Collaboration, R.Aaij et al., Submitted to EPJ C, arXiv:1103.0423

b cross section: J/ψ’sLHCb Collaboration, R.Aaij et al.,

Submitted to EPJ C, arXiv:1103.0423

Large tz bkgd: from semi-lep b

See also: Jibo He, Wednesday 10:00,J/ψ cross section (incl. B→J/ψX) and J/ψ polarization at LHCb

10/29


• Measure pp→bbX through b→J/ψ(μ-μ+)X

LHCb Collaboration, R.Aaij et al., Submitted to EPJ C,

arXiv:1103.0423

b cross section: J/ψ’s

Double differential cross section:

See also: Jibo He, Wednesday 10:00,J/ψ cross section (incl. B→J/ψX) and J/ψ polarization at LHCb

11/29

b cross section at LHCb


• Measure pp→bbX through b→D0Xμν b→J/ψX

• Good agreement among both measurements

LHCb Collaboration, R.Aaij et al., Phys.Lett.B694:209-216,2010, arXiv:1009.2731


Cacciari, Nason, Frixione, Mangano, Ridolfi

(MCFM v5.8, Campbell, Ellis)√s=7 TeV LHCb

5.1 pb-1J/ from b

BR(b→J/ X) =1.16%Assuming frag. fractions from LEPLHCb 15.1 nb-1


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yJ/

NB: both measurements have many correlated errors, e.g. luminosity (10%), tracking eff.(8%), etc.

b

b cross section at LHCb


• Measure pp→bbX through b→D0Xμν b→J/ψX

• Good agreement among both measurements• Good agreement with QCD predictions


LHCb Collaboration, R.Aaij et al., Phys.Lett.B694:209-216,2010, arXiv:1009.2731

(MCFM v5.8, Campbell, Ellis)

13/29

LHCb 15.1 nb-1

b

Cacciari, Nason, Frixione, Mangano, Ridolfie.g. hep-ph/9803400


Cacciari, Nason, Frixione, Mangano, Ridolfi

Motivation

b cross section:• Comparison to QCD predictions• Knowledge of b-yield to ascertain sensitivities in B-physics analyses

Fragmentation fractions, fs/fd:• Input to e.g. inclusive b cross section measurement• Needed for all Bs

0 branching ratios In particular BR(B0

s→ μ+μ-)

Two methods:1) Semi-leptonic: B0/+

(s) → D(s)

+/0 X μν2) Hadronic: B0

(s) → D(s)- π+/K


Motivation: BR(B0s→μμ)


Branching Ratio very sensitive to NP models

BR strongly enhanced in MSSM at large tanβ: tan6/mA

4

A.Buras, G.Isidori, P.ParadisiPhys.Lett.B694:402-409,2011

E.g. G.Isidori & P.Paradisi , Phys.Lett.B639:499-507,2006.

BR(B0s→μμ) determined by normalizing wrt. known

decay: fd/fs: Largest uncertaintyin BR determination

See also: Matteo Palutan, Thuesday 9:00Bs →μμ, B →K*μ and B →sγ at LHCb

15/29

fd/fs: in principle environment dependentLHCb needs to measure it

Ratio of fragmentation fractions fs/fdSemi-leptonic


Strategy:

Uncertainties:• Branching ratio BR(Ds)• Bs detection eff• BR(Bs→D0KXμν)• Tracking, PID, Trigger

efficiency

D0

D+

Ds+

LHCb, 3 pb-1

N(D0) from b: 28474±190

N(D+) from b: 9406±105

N(Ds+) from b: 2208±61

Updated results expected soon

Extra: BR(Bs0→Ds2*-Xμ+ν)

first observation



Phys.Lett.B698:14-20,2011, arXiv:1102.0348

Ds2*+(2573)

m(Ds2*+)=2569.4±1.6 MeV

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Ratio of fragmentation fractions fs/fd

Novel Method• Find decay that is

Theoretically well understood Experimentally clean

Bs→Ds-π+ and B0→D-K+

• U-spin related decays• Pure tree diagrams, factorization expected to work well

• Factorization OK to ~10% (branching ratio level, estimated from data)• Non-factorizable U-spin breaking effects <2% (estimated from data)

Ratio of form factors can be improved• U-spin breaking effects: ~16-32% effect (branching ratio level) • Need to know to relative 20% ( lattice QCD? ) to match experiment


Blasi, et al Phys.Rev. D49 (1994) 238-246

R. Fleischer, N. Serra, N.T, Phys.Rev.D82:034038,2010

• Find decay that is Theoretically well understood Experimentally clean

Bs→Ds-π+ and B0→D-K+


• Na =1.00±0.02 Non-factorizable U-spin breaking effects <2% (estimated from data)

• NF=1.24±0.08 Need to know to relative 20% to match experiment ( lattice QCD?)

Blasi, Colangelo, Nardulli, PaverPhys.Rev. D49 (1994) 238-246, hep-ph/9307290


Novel Method


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• Find decay that is Theoretically well understood Experimentally clean

Bs→Ds-π+ and B0→D-π+


• Na =1.00±0.02 Non-factorizable U-spin breaking effects <2% (estimated from data)

• NF=1.24±0.08 Need to know to relative 20% to match experiment• NE=0.966±0.075 Extra correction due to exchange diagram:

π

d

π π π



Novel Method (2)

20/29


Measurement of N(B0→D-K+) and N(Bs

0→Ds-π+)

• Data set: 35 pb-1 from 2010• Multivariate selection• Likelihood fit to m(KKππ)• Special care for misidentified B0→D-(π→K+)

background:


N(B0→D-K+)=253±21 B0→D-(π+→K)

21/29

Bd→Dπ

Measurement of N(B0→D-K+) and N(Bs

0→Ds-π+)

• Data set: 35 pb-1 from 2010• Multivariate selection• Likelihood fit to m(KKππ)• Special care for misidentified B0→D-(π→K+)

background


N(B0→D-K+)=253±21 N(Bs0→Ds

-π+)=670±34

22/29

Measurement of N(B0→D-π+) and N(Bs

0→Ds-π+)

• Data set: 35 pb-1 from 2010• Multivariate selection• Likelihood fit to m(Kπππ)


N(B0→D-π+)=4109±75 N(Bs0→Ds

-π+)=670±34

23/29

Measurement of N(B0→D-π+) and N(Bs

0→Ds-π+)

• Data set: 35 pb-1 from 2010• Multivariate selection• Likelihood fit to m(Kπππ)


N(B0→D-π+)=4109±75 N(Bs0→Ds

-π+)=670±34

24/29

Extra: ratio BR(B0→D-K+)/BR(B0→D-π+) world best BR(B0→D-K+) See also: Steve Blusk, Thursday 12:15Bs →DsK and DK states at LHCb



Uncertainties from• Fit • PID calibration• Reconstruction eff. difference K,

π• Branching ratio BR(Ds)

25/29


N(B0→D-K+)=253±21 N(Bs0→Ds

-π+)=670±34N(B0→D-π+)=4109±75

B0→D-K+ B0→D-π+


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N(B0→D-K+)=253±21 N(Bs0→Ds

-π+)=670±34N(B0→D-π+)=4109±75

B0→D-K+ B0→D-π+


( LHCb preliminary )

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Combined:

fs/fd compilation


Disclaimer: private compilation

LHCb 2010Preliminary

(NB: old avg.mix χ)

LHCb B0→DK: fs/fd = 0.242 ± 0.034LHCb B0→Dπ: fs/fd = 0.249 ± 0.035LHCb hadronic: fs/fd = 0.245 ± 0.031 . LHCb semi-leptonic: fs/fd = 0.260 ± 0.027 CDF (La Thuile 2011): fs/fd = 0.269 ± 0.033

(updated semi-lep [PRD77] with BR(Ds→φπ))

HFAG (CDF): fs/fd = 0.327 ± 0.039 (updated Mar 2011, semi-lep + avg.mix.χ) (NB: avg.mix.χ to be updated)

HFAG (LEP): fs/fd = 0.256 ± 0.026 HFAG (ALL): fs/fd = 0.270 ± 0.034

See : Robert Harr, Monday 12:15CDF Measurement of Time-Integrated Mixing:

χold = 0.147 ± 0.011χnew = 0.126 ± 0.008χLEP = 0.1259± 0.0042

http://agenda.infn.it/getFile.py/access?contribId=31&sessionId=5&resId=0&materialId=slides&confId=3080

http://www.slac.stanford.edu/xorg/hfag/osc/end_2009/#FRACT

http://www.slac.stanford.edu/xorg/hfag/osc/end_2009/#FRACZ

http://www.slac.stanford.edu/xorg/hfag/osc/end_2009/#FRAC

fs/fd compilation


Outlook:5σ NP discovery potential of

BR(B0s→μμ)

(with σ(fs/fd)~7% ) down to 2x BRSM R. Fleischer, N. Serra, N.T, Phys.Rev.D82:034038,2010

See also: Matteo Palutan, Thuesday 9:00Bs →μμ, B →K*μ and B →sγ at LHCb

→ σ(fs/fd)~7%

→ σ(fs/fd)~13%

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Summary


B0→D-K+

B0→D-π+

B0→D-Xμ+ ν

Wealth of results from LHCb 2010 running:• b cross section:

σ(pp→bbX) = 284±20±49 μb σ(pp→bbX) = 288± 4±48 μb

• extra's: First observation BR(Bs

0→Ds2*-Xμ+ν) World best BR(B0→D-K+)

• fragmentation fractions, fs/fd: fs/fd = 0.242 ± 0.024 ± 0.018 ± 0.016 fs/fd = 0.249 ± 0.013 ± 0.020 ± 0.025 fs/fd = 0.245 ± 0.017 ± 0.018 ± 0.018 fs/fd = 0.260 ± 0.008 ± 0.026

(stat) (sys) (theo)

b→D0Xμ+ ν

b→J/X

Bs0→Ds2*-Xμ+ν

B0→D-K+

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B0→D-h+

Backups


LHCb Papers



Phys.Lett.B694:209-216,2010, arXiv:1009.2731


Submitted to EPJ C, arXiv:1103.0423


Phys.Lett.B698:14-20,2011, arXiv:1102.0348

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fs/fd compilation


HFAG March 2011:

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Factorization

Factorization works to better then 5% Deviation from semileptonic rate is small

Na under control

5 Apr 2011


b cross section and fs/fd at LHCb 34/29

fd/fs from CDFFactorization and SU(3) symmetry OK1) Deviation from semi-leptonic rate is small2) d↔s symmetry OK (compare B→DK and B→Dπ)3) Can even use B0→D+π- instead of B0→D+K-

5 Apr 2011

CDF (PDG)

CDF (FST)


CDF, Phys. Rev. Lett. 98 (2007) 061802

b cross section and fs/fd at LHCb 35/29

b Production Cross Section and Fragmentation Fractions at LHCb

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