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Prospects of search for New Physics in B decays at LHC

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## Prospects of search for New Physics in B decays at LHC

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ITEP / Moscow

Prospects of search for New Physics

in B decays at LHC

- In CP - violation
- In rare decays

Andrey Golutvin Moriond 2007

Mean values of angles and sides of UT are

entirely consistent with SM predictions

Inputs:

Accuracy of angles

is limited by experiment:

- = ±13°
- b = ± 1.5°
- = ± 25°

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

3

Standard strategy to search for New Physics

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 computed

values for

with direct measurements in the processes involving loop graphs.

Interpret the difference as a signal of NP

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 error

propagation: 3° window in corresponds to (245)° window in

5

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 will

effectively constrain Rt and thus

calibrate the lattice calculation

of the parameter

q1

b

q

b

u, c, t

q2

W−

d, s

mbγL+mqγR

W −

W −

d (s)

d (s)

b

u,c,t

b

u, c, t

l+

q

g

Z, γ

l−

q

Complementary Strategy

trees

Compare experimental observables measured in different topologies:

d-/s- penguins

d-/s- boxes

V*ib

Viq

q

u, c, t

b

W−

W+

u, c, t

q

b

Viq

V*ib

|VtsVtb*| and UT angles: , and

- 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

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

Theoretical input: improved precision of lattice calculations

for B×fB and B,,K* formfactors

Experimental input: precision measurement of BR(BK*, )

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/)

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)

ATLAS: similar to LHCb sensitivity in with 30 /fb

s(s) ~ 0.08 (10/fb, Dms=20/ps, 90k J/ evts)

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

- Electroweak penguins
- Very rare decays Bs,d , e

Experimental challenge: keep backgrounds under control

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

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 orparity-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 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/0609037

Present 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 )

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.

Measuring the photon polarization in

B h1h2h3 decays

The measurement of the photon helicity requires the knowledge of the spin direction

of the s-quark emitted from the penguin loop. Use the correlation between s-spin

and angular momentum of the hadronic system (needs partial-wave analysis !!!)

M.Gronau,Y.Grossman,D.Pirjol,A.Ryd PRL 88, 5, 2002

D.Atwood,T.Gershon,M.Hazumi,A.Soni hep-ph/0701021 v 1

V. Shevchenko paper in preparation

Promising channels for LHCb: Expected yield

per 2 fb-1

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

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

Sensitivity to photon helicity measurement is being studied

s

Bd→ K*mmdecayIn SM, the decay is a

b → s penguin diagram

But NP diagrams could also

contribute at the same level

d

d

Bd

K*

m

g

m

- In addition to the virtual photon,
- there will be Z0 contributions
- Which will add some calculable
- right handed contributions.
- But these could be added to by New Physics
- Resulting in modified angular distributions

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

For 2 fb-1 LHCb expects 7200±2100 signal events .(Uncertainty mostly due to BR)

with a B/S < 0.5

Kreuger, Matias hep-ph/0502060

Prospects for Forward-Backward asymmetry measurements

(see M. John talk)

?

MSSM

Rare decays: Bs→mm(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.

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

10-7

10-8

10-9

CMSSM with this same range of gaugino mass

predicts BR (Bs → m+m-) could be ~ a few 10-9 to 10-7

much higher than SM:

LHCb Sensitivity

(signal+bkg is observed)

Limit at 90% C.L.

(only bkg is observed)

BR (x10-9)

BR (x10-9)

5

Expected CDF+D0 Limit

SM prediction

3

Uncertainty in

bkg prediction

SM prediction

Integrated Luminosity (fb-1)

Integrated Luminosity (fb-1)

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

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