Andrey Golutvin Moriond 2007 1

Prospects of search for New Physicsin B decays at LHC

Andrey GolutvinITEP / Moscow

- In CP - violation - In rare decays

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In CP-violation

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ub

cb

V

V

Inputs:

dm

sm

B

K

sin2

Accuracy of sides is limited by theory:- Extraction of |Vub|- Lattice calculation of

Accuracy of angles is limited by experiment:= ± 13° = ± 1.5° = ± 25°

Mean values of angles and sides of UT are entirely consistent with SM predictions

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Define the apex of UT

using at least 2 independent quantities out of 2 sides:

and 3 angles: , and

Extract quantities Rb and from the tree-mediated processes,

that are expected to be unaffected by NP, and compare computedvalues for

with direct measurements in the processes involving loop graphs.

Interpret the difference as a signal of NP

Standard strategy to search for New Physics

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At present the sensitivity of standard approach is limited due to:

- Theoretical uncertainties in sides - Experimental uncertainties in and angles - Geometry of UT (UT is almost rectangular)

Comparison of precisely measured with is not meaningful due to errorpropagation: 3° window in corresponds to (245)° window in

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Precision comparison of the angle and side Rt is very meaningful !!!

~5% theoretical precision in Rt is adequate to a few degree experimental precision in the angle which should be achievable after 1 year of LHC running

Precision measurement of willeffectively constrain Rt and thuscalibrate the lattice calculationof the parameter

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b q1

d, s

q2W−

qB

g

d (s)

q

q

W −

b u,c,t

b

q

u, c, t

u, c, t

q

bqBqB W+ W−

V*ib Viq

Viq V*ib

trees

d-/s- penguins

d-/s- boxes

mbγ

L+mqγ

R

b q

W–

u, c, t

Z, γ

d (s)

l+

l−

W −

b u, c, t

Compare experimental observables measured in different topologies:

Complementary Strategy

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trees vs box loops vs penguin loops

In trees:

(tree) is measured in B J/Ks (tree) = - (tree) - (tree)(tree) is measured in B J/

Precision measurements of angles in tree topologies should be possible. Eventually LHCb will measure , , and with () ~ 0.5°, () ~ few° and() ~ 1° precision respectively

Theoretical uncertainty in Vub extraction

|VtsVtb*| and UT angles: , and

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For the angles:(theoretically clean)Measure (peng) in B,, (peng) in BKs (peng) in Bs

New heavy particles, which may contribute to d- and s- penguins,would lead to some phase shifts in all three angles:

(NP) = (peng) - (tree) (NP) = (BKs) - (BJ/Ks) (NP) = (B) - (BJ/)

For |VtsVtb*| (at the moment not theoretically clean):

Proposed set of observables

Theoretical input: improved precision of lattice calculations for B×fB and B,,K* formfactorsExperimental input: precision measurement of BR(BK*, )

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Contribution of NP to processes mediated by loops (present status)

To boxes: - vs Rb is limited by theory (~10% precision in Rb) (d-box) - poorly measured at the moment (s-box)

To penguins: - ((NP)) < 30° (d-penguin) - (2(NP)) ~8° (2.6 hint) (s-penguin) - ((NP)) not measured yet (s-penguin)

PS (NP) = (NP)

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Angle Channel Yield* Bbb/S LHCb (2/fb)

Bd J/Ψ KS

Bd KS

216k

0.8k

0.8

<2.4

σ() ≈ 0.6°

σ() ≈ 12°

s

Bs J/ΨΦ Bs J/Ψη

Bs ηcΦ

Bs ΦΦ

125k

12k

3k

0.3

2-3

0.7

σ(s) ≈ 1.2°

σ(s) ≈ 6°

(2° with 10/fb)

Bs DsK

Bd D0(K-+)K*0

Bd D0(K+-)K*0

Bd DCP(K+K-)K*

B- D0(K+-)K-

B- D0(K-+)K-

5.4k

0.5k

2.4k

0.6k

60k

2k

<1.0

<0.3

<2.0

<0.3

0.5

0.5

σ() ≈ 13°

σ() ≈ 8°

σ() ≈ 4°-13°

Bd 14k 0.8 σ() < 10°

ATLAS: similar to LHCb sensitivity in with 30 /fb (s) ~ 0.08 (10/fb, ms=20/ps, 90k J/ evts)

CMS: (s) ~ 0.07 (10/fb, on J/ evts, no tagging)

LH

Cb

(see

M.J

ohn

talk

)

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In Rare Decays

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- Radiative penguins

- Electroweak penguins

- Very rare decays Bs,d , e

Experimental challenge: keep backgrounds under control

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Exclusive radiativepenguins

LHCb control channel: Bd K*

~75k signal events per 2fb-1

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Radiative Penguin Decays

Measurement of the photon helicity is very sensitive test of SM

Methods:

- mixing induced CP asymmetries in Bs , BKs 0

- b : asymmetries in the final states angular distributions are

sensitive to the photon and b polarizations.

- Photon helicity can be measured directly using converted photons in BK* decay or parity-odd triple correlation (P(),[ P(h1) P(h2)]) between photon and 2 out of 3

final state hadrons. Good examples are B K and B K decays

b (L) + (ms/mb) (R)

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Polarized b decays: b (1115) (1115) p violates pariry

Assuming b polarization > 20% LHCb can measure (R) component down to 20% (in 1 years of data taking). Limitation - low annual yield (~675 events) requires efficient performance of tracking system.

Mixing induced CP asymmetries

- B BKs0 (B-factories)

S = - (2+O(s))sin(2)ms/mb + (possible contribution from bsg) = - 0.022 ± 0.015

P.Ball and R.Zwicky hep-ph/0609037Present accuracy: S = - 0.21 ± 0.40 (BaBar : 232M BB) S = - 0.10 ± 0.31 (BELLE: 535M BB)

- Bs ( LHCb annual yield ~11 k , B/S ~0.6 )

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Measuring the photon polarization in

B h1h2h3 decays

The measurement of the photon helicity requires the knowledge of the spin directionof the s-quark emitted from the penguin loop. Use the correlation between s-spinand angular momentum of the hadronic system (needs partial-wave analysis !!!)

Promising channels for LHCb: Expected yield per 2 fb-1

BR(B+ K+-+) ~ 2.5 10-5 rich pattern of resonances ~60k

BR(B+ K+) ~ 3 10-6 highly distinctive final state ~ 7k

Sensitivity to photon helicity measurement is being studied

M.Gronau,Y.Grossman,D.Pirjol,A.Ryd PRL 88, 5, 2002D.Atwood,T.Gershon,M.Hazumi,A.Soni hep-ph/0701021 v 1V. Shevchenko paper in preparation

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Bd → K*decay

Bd

sb

K*

In SM, the decay is a b → s penguin diagram

But NP diagrams could also contribute at the same level

d d

For 2 fb-1 LHCb expects 7200±2100 signal events .(Uncertainty mostly due to BR) with a B/S < 0.5

Branching ratio:(1.22+0.38 -0.32) 10-6

n addition to the virtual photon, there will be Z0 contributionsWhich will add some calculable right handed contributions.But these could be added to by New PhysicsResulting in modified angular distributions

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Kreuger, Matias hep-ph/0502060

Prospects for Forward-Backward asymmetry measurements (see M. John talk)

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LHCb prospects

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Rare decays: Bs → for LHCb prospects see M. John talk)

Very small branching ratio in SM:

(3.4 ± 0.5) x 10-9

Present limit from Tevatron at 95% CL(1 fb-1):

< 7 x 10 -8

Expected final limit at 95% CL (8 fb-1):

< 2 x 10 -8

Sensitive to New Physics through loops

Could be strongly enhanced by SUSY.

W

W

b

s

t

?

?

MSSM

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Example: constrained minimal SSM: CMSSM

Anomalous magnetic moment of muon:Measured at BNL, disagrees with SM at 2.7.

am = (25.2 ±9.2) 10-10.

To explain it with CMSSM: for different A0 and tan:250 < m1/2 (gaugino mass) < 650 GeV

CMSSM with this same range of gaugino masspredicts BR (Bs → m+m-) could be ~ a few 10-9 to 10-7

much higher than SM:

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LHC ProspectsLimit at 90% C.L. (only bkg is observed)

Integrated Luminosity (fb-1)

BR

(x1

0-9)

Uncertainty in bkg prediction

Expected CDF+D0 Limit

SM prediction

LHCb Sensitivity(signal+bkg is observed)

Integrated Luminosity (fb-1)

BR

(x1

0-9)

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3SM prediction

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Important measurements to test SM and Search for NP

In CP-violation:

vs Rb and vs Rt (Input from theory !) : if non-zero NP in boxes

(NP), (NP) and (NP): if non-zero NP in penguins

In rare decays:

-Photon helicity in exclusive radiative penguins

- Measurement of FBA, zero point, transversity amplitudes in Bsll exclusive decays (K*, , …)

- Measurement of BR(B s,d ) down to SM predictions

- Search for lepton flavor violation