1

LHCb resultsHugo Ruiz

On behalf of the LHCb Collaboration

Institut de Ciències del Cosmos

PLANCK‘2011, May-June 2011, Lisboa

2

The LHCb physics scope

• ATLAS, CMS: direct search

• LHCb: look for effect of new massive particles in lower energy observables– Many low energy constraints NP will probably show up in loop processes

• New particles can distort the SM (CKM) picture of B decays by modifying:

– Phases CP violation– Amplitudes branching ratios– Lorentz Structure angular distributions

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LHCb: B physics at a pp collider

• And: not too many primary collisions design lumi 2·1032 cm-2s-1

• Signal-background separation:– Invariant mass– Secondary vertices, IP– Particle Id (p-K, etc)

<L> ~ 8 mm

IP

• CP violation studies:

– Event-by-event lifetime– B flavour @ production

Primary pp collision

~ 50 tracks

Signal B

Tagging Bm±K±

K±, p±, m±…

VELORICH

4

MUON

CALORICH2

T

MAGNET

RICH1

VELO

TT

LHCb: B physics at a pp collider

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Data taking in 2010 (and 2011)

• CDF&D0 > 6000 pb-1

– But: x-sect (x3), acceptance, trigger, vertex resol., pID, flavour tagging

• LHCb prospects: – 1 fb-1 by end 2011 (2010 x 27)

2010: 42 pb-1 delivered 37 pb-1 collected (±10%) results in this talk

Design lumi since May 1st! But with ¼ of bunches

2011 : 150 pb-1 delivered 130 pb-1 collected

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Vertexing Tracking

Hit residuals

sm(J/ym+m-) = 13.3 MeV

(12.1 in MC)

s(IP

x) tr

ack

(mm

)

stB ~ 60 fs (~40 fs from MC), work in progressoscillation period Bd(Bs) ~12500(350) fs

s(Z)

ver

tex

(mm

)

# tracks

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Particle identification

fK+K- D K+p- from D*

Ksp+p- Lp+p-

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Production & spectroscopy

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Z production (16.5 pb-1)

LHCb-CONF-2011-012

x: fract. of pbeamcarried by colliding partonQ2: squared p transfer in partonic collision

ATLAS CMS

ds/dh

(pb)

hZ

Trigger: pT(m)>10GeV

Main syst: lumi LHCb preliminary

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W production (16.5 pb-1)

W-

W+

• Selection: lepton + global event (ΣM<20GeV, ΣPT<10GeV)

Acceptance of GPDsATLAS, CMS

Trigger: pT(m)>10GeV

LHCb-CONF-2011-012

Z&W data vs models:

LHCb preliminary

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J/y production (5.2 pb-1)

• Interesting: no model describes both dsJ/y/dpT

and J/y polarization from Tevatron

• LHCb: >0.5M J/y’s, no life-time bias @trigger• Measured both in 5 bins of h and 14 of pT

• Prompt and from-B separated using pseudo-lifetime

Eur. Phys. J. C 71 (2011) 1645

One bin!

Prompt J/y production

Main systs: lumi, J/y polarization, etracking

from bOne bin!

prompt

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sbb

• Method 1: from J/y – From “long-lived” component in J/y analysis– Extrapolated to 4p:

spp = 288 ± 4 ± 48 mb

• Method 2: through b→D0(→K-π+)Xμ-ν(uses BRs of B0D*-Xμ+ν D0Yμ+ν, B+ D0Xμ+ν, B0

s Ds*-Xμ+νD0Yμ+ν)

– Extrapolated to 4p:

spp = 284 ± 20 ± 49 mb

• Good agreement between both– though correlated errors: lumi, etracking, etc)

Phys. Lett. B 694 (2010) 209

Main systs: lumi, etracking

Black, violet: 2 subsamples with different triggerRed: combination

Theoretical error

(e.g. mb and μR,F)

Cacciari, et al., NL0 + resum of pT logs to NLO , e.g. hep-ph/9803400

(NLO, MCFM v5.8, Campbell, Ellis)

Eur. Phys. J. C 71 (2011) 1645

Additional syst.: BR(b→J/y X)

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fs/fd

• Required for normalizing new Bs BRs with precisely-measured Bd BRs from B factories, current uncertainty 13%

• Use decays of Bs and B0 with:– Precise theoretical prediction of ratio of BRs – same kinematics cancellation of systematics

LHCb-CONF-2011-013

Same particles in final stateTheo. uncert. 9%

Theo. uncert. 7%

Main syst: BR(Ds+KKp), 5%

B0 D-(K+p-p-)p+B0 D-(K+p-p-)K+ BsDs-(K+K-p-)p +

LHCb preliminary

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Mass of X(3872)• Mass far from expected from conventional charmonium state• Exotic alternatives: D*D0 molecule, tetraquark

Main systs: p scale, E loss correction, TT alignement

LHCb-CONF-2011-021

LHCb preliminary

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Towards CP violation

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CP violation

• Bd sector extensively studied at B factories– CKM is basically OK

• Lacking precise direct measurement of g

•Required modes too rare (B fact. yield 10-4LHCb)•g will provide many new tests of SM

• Bs sector only accessed by Tevatron– Lacking a precise measurement of the Bs mixing phase– Penguins unexplored!

• Some hints of NP:– Like-sign di-m charge asymmetry hints for NP in mixing,

sin2b…

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Direct CP violation in B0/Bs K-p+

LHCb:

LHCb-CONF-2011-11

Bs

Not corrected for det. & prod. asymm.

We had to control potential sources of fake CP violation:• Detector: from many D decays, magnet up & down, using known CP violation

• Production: from B+J/y(m+m-)K- + MC correction for B+B0

Before LHCb

~9σ CP viol. not yet stablished

Bd

LHCb preliminary

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g from tree processes• Time-independent methods: same final state

through crossed D decay (GLW, ADS, GGSZ…)

– Main challenge: BRs in suppressed modes

• Enhancing statistics:

– Measured relative BRs withworld-best precisions!

– Proved we can do physics with 6 track decays

B-D0K-

+p+p-

LHCb-CONF-2011-07

LHCb preliminary

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Flavour tagging & Dmd

• Optimized using real data:

LHCb-CONF-2011-03LHCb-CONF-2011-10

Signal B

Tagging B

PV

lepton (m±, e±)

kaon (K±)

Dx

hadron from fragmentation or B** decay (K±, p±)

Same side (SS)

Opposite side (OS)

vertex charge

Channel eefftag

B0D*-μ+ν 2.87±0.32%

B+J/yK+ 2.38±0.33%

B0J/yK* 2.82±0.87%

Dmd fixed to pdg value

Main systs: z scale, p scale (to 0.1%, due to B, align.)

LHCb preliminary

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Dms• Used 1300 events:

• Fit with event-by-event values of st (36-44 fs) & mistag prob.– eeff

tag = 3.8 ± 2.1 % (OS only)– Mixing signal at 4.6s level

• CDF:• LHCb:

LHCb-CONF-2011-05

LHCb preliminary

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Towards fs with Bs J/yf• Golden channel:

• Acceptances are a key issue, benchmarked by measuring: a) B meson lifetimes b) Polarization amplitudes

Time-unbiased trigger only

Final state combines CP even-odd need to disentangle polariz. amplitudes angular analysis

All consistent with world valuesLHCb-CONF-2011-01 LHCb-CONF-2011-02

st 50 fs

LHCb preliminary LHCb preliminary

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fs: first results from Bs J/yf• 757±28 events (t>0.3ps)• 7D fit (m,t,tag,η,φ,ψ,θ)• No point-estimate yet• Include statistical uncertainty &

systematics from tagging and Δms

– All other systematycs << stat. uncert.

• Comparison with CDF:

Expect world-best fs measurement with 2011 data!

LHCb 36pb-1 CDF 5.2fb-1

Events 750 6500

st (fs) 50 100

OS eefftag (%) 2.2±0.5 1.2±0.2

SS eefftag (%) Not enough

stats to calib. 3.5±1.4

SM

LHCb preliminary

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1st observation of Bs decays

• Bs→J/ψf0(980) (33 pb-1 )– fs (as J/yf), no need for angular analysis

• Bs→K*0K*0

– fs & g through Bs penguin, Bd → fKs

• Bs→D0K*0

– Bckgrd for g from trees from BDK

• Bs→Ds2*(2573)+m-n (20pb-1)

– Start exploration of D reson. in Bs syst.

PLB 698 (2011) 115

LHCb-CONF-2011-019

PLB 698 (2011) 14

LHCb-CONF-2011-08

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Rare B decays

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Bd K*m+m-

• Golden observable:

•LHCb:

–Good data-MC agreement–Expect to be competitive with 300 pb-1

Rarest decay seen: B±K ±m+m- (BR 5 · 10-7)

BR 10-6

Useful to test SM prediction of BR(BKee) / BR(K Kmm)

Nσ = 5.5

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B0/Bs m+m-

• Double suppression: FCNC & helicity• Precise SM prediction:

Bsμ+μ- = (3.2±0.2)×10-9

B0μ+μ- = (1.0±0.1)×10-10

A.J.Buras, arXiv:1012.1447, E.Gamiz et al. Phys.Rev.D 80 (2009) 014503

• Sensitive to NP in scalar/pseudo-scalar sector: MSSM, large tanβ approximation

BR(Bs,dμ+μ- ) ∝ tan6β/M4A

• Results are competitive with world bests:

Phys. Lett. B 699 (2011) 330

BR(Bs→μμ) < 4.3 (5.6)×10-8 at 90% (95%) CLCDF BR(Bs→μμ) < 4.3×10-8 at 95% CL

3.7 fb-1 Public note 9892 (2009)D0 BR(Bs→μμ) < 5.1×10-8 at 95% CL

6.1 fb-1 Phys. Lett. B 693 (2010)

BR(B0→μμ) < 1.2 (1.5)×10-8 at 90% (95%) CLCDF BR(Bd→μμ)<0.76×10-8 at 95% CL

3.7 fb-1 Public note 9892 (2009)

Bs m+m-

B0 m+m-

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Bs m+m-: prospects

LHCb will either find signs of NP orexclude large regions of SUSY parameters with 2010/11 data

NUMH1 (O. Buchmuller et al, EPJ C64 (2009))

Compatible regions

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Conclusions• LHCb has successfully:

– Started exploration of terra incognita:• Proton PDFs• Flavour production• Spectroscopy• Bs and Bd BRs

– Produced world-class measurements• Dms

• Limits on BR(Bmm)– Demonstrated its capability to find NP with 2010/11 data:

• g• fs

• BR(Bmm)• B0K*mm• ...

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Back-up

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U production

CMSLHCb

Main systs: etrigger, U polariz.

Um+m-

LHCb-CONF-2011-017

• Interesting for QCD because heavy-quark state, challenging because fc 0.2 %

• Total of 2.2K candidates (in 3 modes) from Tevatron

• 43±13 in LHCb…

Bc±J/yp ±

Bc+ production

Main systs: Bc

± lifetime

LHCb-CONF-2011-016

• In addition: double J/y

LHCb-CONF-2011-009

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1st observation of Cabibbo-suppressed decays

• BR’s measured relative to Cabibbo-favoured modes:

LHCb-CONF-2011-24

Expect dg/g 5 with 2011/12 data

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Rare decays• Interesting decays at the limit of statistical reach of B factories

and Tevatron• Some examples:

BsfgBR NP affects:

Right-handed operators g polarization CP viol. in mixing appears

Bsm+m-TeVatron @90%CL (2fb1)

< 4510-9

SM: dBR/BR 10% sensitive to new scalar & pseudoscalar interactions

MSSM: BR tan6β/MA4

5·10-5

g gZ, Z,m+

m-

m+

m-

m+

m-t

B0K*m+m- 10-6Angular distributions sensitive to several new operators

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Branching ratios Production studies

• B factories @ U(4s) measured Bd BRs with precisions 2.5-5%– Could count numbers of produced B

• At Tevatron, LHC: non-straight-forward production mechanisms use B-factory measured BRs for nomalization

• To normalize Bs using Bd one needs ratio of b quarks hadronizing to Bs over Bd (fs/fd)– CDF (La Thuile 2011): fs/fd = 0.269 ±

0.033– HFAG (ALL): fs/fd = 0.270 ± 0.034

13% relative error

• h coverage complementary to that of ATLAS and CMS

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Running conditions

• LHCb prefers moderate luminosity to avoid multiple pp interactions / crossing– They complicate handling of secondary vertices

• 2010 and 2011 conditions far beyond nominal:

Design

m

# in

tera

ction

s/cr

ossin

g

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D0 flavor-specific asymmetry

• Inclusive method not fit for LHC, with expected production asymmetry 1%.

• Solution: measure difference, where this and other effects cancel

D0

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Fragmentation functions: semileptonic 3pb-1

• Uncertainties:• Branching ratio BR(Ds)

• Bs detection eff• BR(Bs→D0KXμν)• Tracking, PID, Trigger efficiency

Updated results expected soon

D0

D+

Ds+

N(D0) from b: 28474±190

N(D+) from b: 9406±105

N(Ds+) from b: 2208±61

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fs at Tevatron