lhcb results
DESCRIPTION
LHCb Collaboration: 755 M embers, from 55 Institutes in 15 Countries. LHCb results. Evgeny Gushchin (INR RAS) for the LHCb collaboration. Outline. Introduction LHC as B-factory LHCb is B-meson experiment for search NP in CPV and rare decays Experimental technique and key performances - PowerPoint PPT PresentationTRANSCRIPT
LHCb results
Evgeny Gushchin
(INR RAS)
for the LHCb collaboration
LHCb Collaboration:755 Members, from 55 Institutes in 15 Countries
XV Lomonosov conference, Moscow
Outline
• Introduction– LHC as B-factory
• LHCb is B-meson experiment for search NP in CPV and rare decays– Experimental technique and key performances
• Physics program and selected Results• Conclusion
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Search for New Physics beyond SM at LHC
Search for new particles with observable masses produced directly in pp collisions
As virtual contribution of new heavy particles i.e. to loop and box diagrams in FCNC : i.e. it can change values, phases and/or Lorentz structure of couplings.
i.e. Higgs, SupersymmetryAND/OR
measurable as deviation from SM precise prediction for heavy quark processes, i.e. for B,D mesons:
• in rare decays • in CP violation phase (mixing and decay)
Very good statistics:Very large bb-production
Very good detector:– Selective/efficient trigger– PID– Excellent mass and time
resolution
LHCb @ LHC!!!
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LHC as B - factory
• Very high luminosity – 2.4*1033(nominal-1034)cm-2sec-1
• High production cross-section (@3.5TeV):– ~300µb ( pp bb X) and ~6.1mb ( pp cc X)
– But also ~65 mb for minimum-bias
• Annual yield (in LHCb) – > 1011BB-pair and 20xDD.
To reduce L0 rate > 10 MHz to 2-3 kHz VERY selective trigger is necessary!Trigger on low pT tracks with efficient PID
Tevatron: instant luminosity reached ~4*1032/cm2/s and total L~11/fb. Cross-sections bb is 3 times lower than at LHC.
B-pairs are produced mainly in forward and backward directions:
Single-arm spectrometer covering ~4% of open angle has ~40% acceptance.
All b-species: B+ : B0 : B0
s : Λ0b : Bc
40%:40%:10%:10%:0.1%
In LHCb:~1 of 200 collisions with b-quark !~1 of 10 - with c-quark !
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LHCb detectorLHCb is forward spectrometer optimized for studies of CPV and B-meson rare decays
LHCb key performances:Vertex/proper time resolution : VELOPID: RICH, Calorimeter, Muon systemMass resolution: Tracker
~4Tm
p-p interaction point
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LHCb detector and trigger efficiency
Detector subsystems are ~99% efficient!
Trigger has very high selection efficiency!
Muon trigger (J/) eff ~ 95%Hadron trigger (D0) eff ~ 60%
PT PT PT
L0e,
L0had
L0
High pT trackNon-zero impact parameter
HARDWARE
SOFTWARE
Inclusive selections:, , +track,
charm, ..+ Exclusive selections
Global reconstruction
Storage3 kHz
30 kHz
40 MHz
<1 MHz
Lev
el-0
HL
T1
HL
T2
Average event size ~35 kB
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Vertex / Time resolutionLHCb lifetime measurements using 36 pb-1 of 2010 data – world class!
1.638 ± 0.0111.525 ± 0.0091.525 ± 0.0091.477 ± 0.0461.391 ± 0.038
PDG [ps]LHCb-CONF-2011-001 [ps]
Vertex Locator (VELO)provides excellent proper time resolution of ~50 fs
Both statistical and systematical errors are expected to be significantly improved with 2011 data!
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Mass resolutionMass resolution is based on precise momentum measurement with LHCb magnet and
tracker: Δp/p<0.5% up to 100 GeV/c
LHCb-CONF-2011-027: masses [MeV/c2]5279.17 ±
0.295279.50 ± 0.305279.50 ± 0.305366.30 ± 0.605620.2 ± 1.66277 ± 6
PDG [MeV/c2]
Bu+ J/ψ K+ Bs
0 J/ψ φ
2010 L=35 pb-1
World-best mass measurements!
With 2010 data!
2010 L=35 pb-1
11151±115 events
=10.50±0.10 MeV/c2
816±30 events
= 6.96±0.25 MeV/c2
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Particle Identification
Hadron PID – RICH1 and RICH2
Muon PID – Muon systemphoton/electron/hadron PID –
SPD/PRS/ECAL/HCAL
0 (no conversions)
X
RICH PID absolutely necessary to identify charged hadrons in B hh
E = 7.2 MeV/c2
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LHCb operationLHCb collected ~37 pb-1 in 2010 and already ~ 700 pb-1 recorded in 2011By end of 2011 LHCb hopes to collect 1 fb-1
nominal µ =0.4
•LHC reached nominal peak luminosity of 2.4*1033 cm-2s-1 with number of bunches is ~1300 from ~2600.•LHCb recording >1pb-1/hour running at L~3.5*1032 cm-2sec-1 in auto-leveling mode•GPD luminosity is 4 times higher than LHCb
•Visual average number of vertexes per BX now is ~3 times larger than nominal µ =0.4 (in 2010 ~6
larger)•1 PV gives ~30 tracks/rapidity unit •Higher µ means higher track multiplicity, that is dangerous for reconstruction
LHCb luminosity auto-leveling
LHC performs well!
~30 pb-1 for LHCb in 29 h in single fill !dL/dt ~ 100 pb-1/week !
2010
nominal µ =0.4
2011
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LHCb physics program and key measurements
LHCb is optimized for study of CP-violation and rare decays in B-mesons.
LHCb physics program includes measurements:• CP-violation in B+,B0,Bs
– Prospects for -angle measurement• Tree-level processes (B DX),• Loop processes (charmless B decays)
– Direct CP-violation (B K)– Mixing induced CPV ( s )
• Rare decays &NP– Bd → K*µµ– Bs → µµ – …
• Quarkonia studies• Physics with charm • Soft QCD• Electroweak physics (W,Z)
More studies are presented today in LHCb talks by Vladislav Balagura, Pavel Krokovny and Dasha Savrina
Highlights in this talk
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CKM – matrix is measured very precisely. Great jobs done by B-factories and others.Less constrained -angle :
combinated “trees” & “loops”: = (67±4)°from “trees” only: = (73+22
-25)°
Prospects for -measurements with “trees”:(based on Gronau-London-Wyler & Atwood-Dunietz-Soni methods+ time-dependent + Dalitz-plot analysis )
• To combine Bs Ds± K±, B0 DK*0 and B±DK±
()~5° with 2 fb-1
Bs Ds-K+ (Ds
+K-) decays • under study, time-dependent analysis (Acp - M)• M – Bs mixing phase well constrained in Bs→Ј/ψФ
- at first step ∆ms measurement using Bs Ds
B±DK± decays using common mode for D0&D0 K+-
Mode more suppressed for D0 and favored for D0
maximizes interference: D0 K+- (DCS) and D0 K+- (CF)
But total branching very small (~10-7)
Preliminary: evidence for suppressed ADS mode at 4.0 with 343 pb-1.Ratio to favored mode:
-angle measurements
“trees”
World average (without LHCb):1.6 ± 0.3
-0.58 ± 0.21
PL
B27
0,75
(199
1);
PR
L78
,325
7(19
97)
World-class measurement!
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Measurement of ∆ms
• ∆ms – mixing frequency in Bs
• Used ~1381 B0s decays from 2010 data:
• Combining the 4 decays allows suppress decay-specific features
• To be used in time-dependent CPV studies
Likelihood scan for ∆ms
LHCb-CONF-2011-005, CERN-PAPER-2011-010
World-class measurement!
World average: ∆ms = 17.77 ± 0.10 ± 0.07 ps-1
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Direct CP asymmetry measurement in B0d,s→K
LHCb with L=320pb-1 of 2011 data already has done:B0→K - the most precise single measurement and first 5σ observation at
hadron machine! B0
s→K - the first evidence of CP-violation in Bs decay!
LHCb-CONF-2011-042Acp(B
0→Kπ) = -0.088±0.011(stat) ±0.008(syst)
To be compared with world average: -0.098+0.012-0.011
Acp(Bs→Kπ) = 0.27±0.08(stat) ±0.02(syst)
First LHCb result (with 37pb-1 data of 2010)
LHCb-CONF-2011-011
Acp(B0→K+π0.074±0.033- =(־(stat) ±0.008(syst)
Acp(B0
s→K־ π+)= -0.15±0.19(stat) ±0.02(syst)
HFAG:
Acp(B0→K+π־)= - 0.098+0.012
-0.011
CDF:
Acp(B0
s→K־ π+)= 0.39±0.15(stat) ±0.08(syst)
Raw asymmetry (has to be corrected for
detector and production asymmetry)
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LHCb result on fs/fd
Very important for absolute branchingmeasurements like Bs
The ratio of fragmentation fractions fs/fd is measured by LHCb:
• In hadronic decays, via relative abundance of B0
s→D־s+ to B0→D־K+ and B0→D־+
LHCb-PAPER-2011-006, submit. To PRL
• In semileptonic decays
LHCb-CONF-2011-028
• And combined result
LHCb-CONF-2011-034
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Quarkonium studies
LHCb quarkonium physics program is rich and promising:• Heavy quarkonium states
– give impact to theory (NRQCD..)
– exotic states: molecular type state, tetraquark (?)
• + Related production studies – test QCD models in forward region
• Highlights : X(3872), X(4140), χc , χb
• New exciting results are expected in future: (2S) and (3S) production
– J/ polarization (pT,y)
– X(3872) quantum numbers and precise mass
– Z±(4430) confirmation and Zb existence
– New states?
See also Vladislav’s talk today
XV Lomonosov conference, Moscow
Production studies at LHCbMany new results for flavour production were obtained with 2010 data:
• pp b b X• pp J/ X• pp F X W,Z • (1S)
Bc+
• c
• pp J/ J/ X
Test QCD model
(tetraquark?)
LHCb-CONF-2011-012
LHCb-CONF-2011-016
LHCb-CONF-2011-017
LHCb-CONF-2011-020
LHCb-PAPER-2011-013
Test QCD model in Forward region
LHCb-PAPER-2011-007
first observation in p-p collisions
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X(3872) J/ +-
Unknown quantum numbers.Not excluded conventional charmonium state c2(1D), but predicted mass is far bellow.
Can be exotic state: molecular 1++ (D*D0 most popular) or tetraquark.
X(3872) production cross-section (LHCb-CONF-2011-043)
Mass measurement X(3872) (LHCb-CONF-2011-021)
MX(3872) = 3871.96 ± 0.46(stat) ± 0.10 (syst) MeV/c2
To test molecular state mass precision has to be <0.1 MeV/c2 – in prompt.Quantum numbers have to be identified in B-decays.
2010 data
Search for X(4140)
CDF observed a 5σ peak in the B+→J/ψ φ K+ channel.
Candidate for exotic bounds state
Preliminary (LHCb-CONF-2011-045)
LHCb with 376 pb-1:
364 ± 20 of B+→J/ψ φ K+ sample after φ –mass cut.
~3.2 times more than CDF with 6fb-1.
Fit (LHCb): 7 ± 5 events
Scaled from CDF data :
39 ± 9 ± 6 events
CDF arXiv:1101.6058
LHCb does not confirm presence of X(4140)
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Production of χcJ/ • P-wave charmonium state
• ECAL only detection of photons:
with/without conversion
• States separation is done by fit of
mass-spectrum with both states χc1 χc2
• 209k χc with 35.6 pb-1 (2010)
LHCb-CONF-2011-020 Test NRQCD: colour singlet + colour octetDiscrepancy at low pT
Observation of b (1S) • In order to interpret measurements of the production and
polarization the feeddown from higher bottomonium states has
to be understood.
• According to Pythia MC, ~ 40% of (1S) come from b.
• A clear signal for b production is seen.
• The photon is reconstructed only with the calorimeter info.• Can not do a separation of the states yet.
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Expecting world best measurements s , Δms soon!
CP-violation phase in Bs-mixing: Bs→Ј/ψФ
Year 2010:Nsig=836 ± 60
LHCb-CONF-2011-006: data from 2010 L=36 pb-1
“Toy” Monte-Carlo using 2010 data as distribution function, but for 10xlarger statistics
Results for 2011 data with much larger statistics are coming very soon
-> expecting world best
measurement of s!
Year 2011:
Standard Model value, probability = 22%(1.2σ)
• Dominant contribution – tree-level diagram• Contribution from “penguin” is small (10-3 – 10-4)
• Interference between direct decay and decay via mixing gives CPV phase: s= M -2D
• In Standard Model s 2 s = -2arg(VtsVtb*/VcsVcb
*) - 0.0363 ± 0.0017 rad
• Search for New Physics in mixing: s= sSM
+sNP
See also Pavel’s talk today
XV Lomonosov conference, Moscow
Other channels relevant for s measurement
“Penguin” diagram dominated can help to control penguin effect in Bs→Ј/ψФ for s extraction :
• Bs→ФФ
• Bs→K*K* - The first observation ! Can help to extract s and
• Bs→Ј/ψK*
• Bs→K+K ־ - Most precise lifetime measurement !
Box diagram dominated can be used for s measurement :
• Bs→Ј/ψf0(980) - The first observation ! CP-odd eigenstate
• Bs→Ј/ψf2’(1525) - The first observation !
Phys. Lett. B 698 (2011) 115
LHCb-CONF-2011-035
LHCb-CONF-2011-018
LHCb-CONF-2011-019
LHCb-CONF-2011-025
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Results are consistent with SM prediction for forward-backward
asymmetry AFB, longitudinal polarization FL and differential
brunching fraction dBF/dq2:
Statistical errors are dominated now and will be improved with
more data. Systematical error is also expected to be improved with
more statistics.
Search for NP in rare decays: Bd → K*µµ • The most known observable sensitive to NP is AFB
• Current status: no evidence of zero-crossing point AFB(q2) predicted in SM
• LHCb can reach precision for ZCP Δq2 < 0.5 GeV2 at 2 fb-1
LHCb with 309 pb-1achieved (preliminary) the most precise measurement to date
LH
Cb
-CO
NF
-201
1-03
8
BaB
ar [
PR
D 7
9 (2
009)
], B
elle
[P
RL
103
(20
09)]
, CD
F [
PR
L 1
06 (
2011
)]
See also Dasha’s talk today
XV Lomonosov conference, Moscow
Prospect: Bs,d → µµ
Prospect on the base of 37 pb-1 (2010):
• ~2 fb-1 will reach exclusion at SM level
• Observation will need more statistics
Golden mode: Bs,d → µµ • Ultra rare decays (FCNC and helicity suppressed)• SM predicts (via box and penguin diagrams):
BR(Bs → µµ) = (3.2 ± 0.2) · 10 -9
BR(Bd → µµ) = (1.1 ± 0.1) · 10 -10
With ~300 pb-1 of LHCb data at SM level after selection:
~3.2 Bs → µµ and ~0.32 Bd → µµ events
CDF reported the observation:
BR(Bs → µµ) = (1.8 +1.1-0.9) · 10 -8
arxiv: 1107.2304
• LHCb presents preliminary result with 300 pb-1
LHCb-CONF-2011-037:
BR(Bs0 → µµ) = 1.3 (1.6) · 10 -8 at 90%(95%)C.L.
BR(B0 → µµ) = 4.2 (5.2) · 10 -9 at 90%(95%)C.L.
• Combining with preliminary result with 37 pb-1
PLB 699(2011) 330,[hep-ex/1103.2165]
BR(Bs0 → µµ) = 1.2 (1.5) · 10 -8 at 90%(95%)C.L.
• Combining with CMS observationLHCb-CONF-2011-047:
BR(Bs0 → µµ) = 0.9 (1.1) · 10 -8 at 90%(95%)C.L.
Excess seen by CDF is not confirmed!~1 fb-1 allows a considerable constrain on MSSM
Most-precise measurement!
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Conclusion• In 2010-2011 LHCb collected more than 700 pb-1 of rich data demonstrating:
– Very good performance of trigger and data taking– Ability to work efficiently in hadronic environment– Ability to work with much larger luminosity than nominal (2 L -instant luminosity
and 6 - PV av. number)!• With 2010 data LHCb already has got competitive results with B-factories and
Tevatron• LHCb provided many world-class measurements:
– First observations of many B-decay modes– Production of heavy flavour quarks and quarkonium states
– World-best single measurement of direct CPV in B0s→K
– World-class measurements of CPV phase s, ∆ms
– Most precise measurements of rare decays Bd → K*µµ, Bs → µµ
• Expecting ~1 fb-1 of data this year and many most-precise measurements very soon!
• LHCb searches for New Physics with unprecedented precision!
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Thank You!
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BACK-UP
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LHCb prospects for upgrade
LHCb sensitivities for key observables
CERN-LHCC-2011-001
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First observations of B-decays in LHCb
• Bs DK* LHCb-CONF-2011-008
• B DK CS-mode, can be used for -measurements LHCb-CONF-2011-024
• B (2s) LHCb-CONF-2011-014 – mixing CP
• Bs J/K* penguin-suppressed LHCb-CONF-2011-025
• Bs K*barK* time-dependent CP LHCb-CONF-2011-019
• PLB 698(2011)14
• Bs J/ f0(980) mixing phase PLB 698(2011)115
• Bs J/ f2’(1525) mixing phase LHCb-CONF-2011-035
• Bc J/ first observation LHCb-CONF-2011-040
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Search for NP effects in Bd → K*µµ
• In SM via FCNC (box and penguin diagrams)
• Helicity structure is sensitive to right-handed and new scalar operators
• The most known observable sensitive to NP is AFB
• Current status: no evidence of zero-crossing point AFB(q2) predicted in SM
• LHCb can reach precision for ZCP Δq2 < 0.5 GeV2 at 2 fb-1
XV Lomonosov conference, Moscow
Results are consistent with SM prediction for
forward-backward asymmetry AFB, longitudinal
polarization FL and differential brunching fraction dBF/dq2:
Statistical errors are dominated now and will improved
with more data. Systematical error is also expected to be
improved with more statistics.
LHCb analysis and results Bd → K*µµ Analysis strategy:• Events selection using Boosted Decision Tree (composition of topological and kinematical observables)• Correction for non-uniformity of reconstruction and selection• MC check with control channels• Validation using Bd→Ј/ψK*
• Fit the angular observables
LHCb with 309 pb-1achieved (preliminary) the most precise measurement to date
BaB
ar [
PR
D 7
9 (2
009)
], B
elle
[P
RL
103
(20
09)]
, CD
F [
PR
L 1
06 (
2011
)]
XV Lomonosov conference, Moscow
CP-violation in Bs mixing: Bs→Ј/ψФ • Dominant contribution – tree-level diagram
• Contribution from “penguin” is small (10-3 – 10-4)
• Interference between direct decay and decay via mixing gives CPV phase: s= M -2D
• In Standard Model s 2 s = -2arg(VtsVtb*/VcsVcb
*) - 0.0363 ± 0.0017 rad
• Search New Physics in mixing: s= sSM
+sNP
Strategy to measure s :
• Trigger and select Bs→Ј/ψФ events
• measure proper time • Measure transversity angles of final decay
products to disentangle CP -odd and –even states• Tag initial flavor
• Fit s with other unknown parameters
LHCb relevant results:LHCb relevant results:• LHCb-CONF-2011-001:
Lifetime measurements of b →Ј/ψX
• LHCb-CONF-2011-005: from Bs→Ds
Δms = 17.63 ± 0.11(stat) ± 0.04(syst)
Flavour tagging studies:Flavour tagging studies:• LHCb-CONF-2011-002:
Bs→Ј/ψФ :
Γs = (0.680 ± 0.034stat ± 0.027syst) ps-1
ΔΓs = (0.084 ± 0.112stat ± 0.021syst) ps-1
• LHCb-CONF-2011-003:
Tagging efficiency measurements• LHCb-CONF-2011-004:
Time dependent analysis B0→Ј/ψKs
Decay D
Mixing M
See also Pavel’s talk today
XV Lomonosov conference, Moscow
Expecting world best measurements s , Δms soon!
CP-violation phase results: Bs→Ј/ψФ
Year 2010:Nsig=836 ± 60
LHCb-CONF-2011-006: data from 2010 L=36 pb-1
“Toy” Monte-Carlo using 2010 data as distribution function, but for 10xlarger statistics
Results for 2011 data with much larger statistics are coming very soon
-> expecting world best
measurement of s!
Year 2011:
Standard Model value, probability = 22%(1.2σ)
XV Lomonosov conference, Moscow
Rare decays: Bs,d → µµ • Ultra rare decays (FCNC and helicity suppressed)• SM predicts (via box and penguin diagrams):
BR(Bs → µµ) = (3.2 ± 0.2) · 10 -9
BR(Bd → µµ) = (1.1 ± 0.1) · 10 -10
CDF reported the observation:
BR(Bs → µµ) = (1.8 +1.1-0.9) · 10 -8
arxiv: 1107.2304
With ~300 pb-1 of LHCb data at SM level after selection:
~3.2 Bs → µµ and ~0.32 Bd → µµ events
• LHCb presents preliminary result with 300 pb-1
LHCb-CONF-2011-037:
BR(Bs0
→ µµ) = 1.3 (1.6) · 10 -8 at 90%(95%)C.L.
BR(B0 → µµ) = 4.2 (5.2) · 10 -9 at 90%(95%)C.L.
• Combining with preliminary result with 37 pb-1
PLB 699(2011) 330,[hep-ex/1103.2165]
BR(Bs0
→ µµ) = 1.2 (1.5) · 10 -8 at 90%(95%)C.L.
• Combining with CMS observationLHCb-CONF-2011-047:
BR(Bs0
→ µµ) = 0.9 (1.1) · 10 -8 at 90%(95%)C.L.
Excess seen by CDF is not confirmed
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Prospect: Bs,d → µµ Prospect on the base of 37 pb-1 (2010):• ~2 fb-1 will reach exclusion at SM level • Observation will need more statistics
~1 fb-1 allows a considerable constrain on MSSM
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LHCb-CONF-2011-019
The first observation of Bs→K*K*
Can help to extract s and
Other channels relevant for s • “Penguin” diagram dominated: Bs→ФФ Bs→K*K* Bs→Ј/ψK* Bs→K+K ־
LHCb-CONF-2011-025
Assuming all events are from K*→K for mass |M(K)-M(K*)|<150 MeV
Can help to control penguin effect in Bs→Ј/ψФ for s extraction
LHCb-CONF-2011-018
Most precise lifetime measurement of Bs→K+K ־
Can be used to put constrains on s and ΔΓs
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Other channels sensitive for s
• Box diagram dominated: Bs→Ј/ψf0(980) Bs→Ј/ψf2’(1525)
Phys. Lett. B 698 (2011) 115
The first observation of Bs→Ј/ψf0(980)
Statistics of 2010 ~34 pb-1
CP odd eigenstate
LHCb-CONF-2011-035
The first observation of Bs→Ј/ψf2’(1525)
Can be used for s measurement
Statistics of 2010 ~34 pb-1 + 125 pb-1 of 2011