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Andrey Golutvin ITEP / Moscow. Prospects of search for New Physics in B decays at LHC. In CP - violation In rare decays. In CP-violation. Mean values of angles and sides of UT are entirely consistent with SM predictions. Inputs:. Accuracy of angles is limited by experiment:

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Prospects of search for New Physics in B decays at LHC


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slide1

Andrey Golutvin

ITEP / Moscow

Prospects of search for New Physics

in B decays at LHC

  • In CP - violation
  • In rare decays

Andrey Golutvin Moriond 2007

slide3

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

slide4

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

slide5

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 (245)° window in 

5

slide6

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

slide7

W–

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

slide8

|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

slide9

Proposed set of observables

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(BK*, )

For the angles:

(theoretically clean)

Measure (peng) in B,,

(peng) in BKs

(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) = (BKs) - (BJ/Ks)

(NP) = (B) - (BJ/)

slide10

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)

slide11

LHCb (see M.John talk)

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)

slide13

Radiative penguins

  • Electroweak penguins
  • Very rare decays Bs,d  , e

Experimental challenge: keep backgrounds under control

slide14

Exclusive radiative

penguins

LHCb control channel: Bd K*

~75k signal events per 2fb-1

13

slide15

Radiative Penguin Decays

b   (L) + (ms/mb)  (R)

Measurement of the photon helicity is very sensitive test of SM

Methods:

-mixing induced CP asymmetries in Bs  , BKs 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 BK* 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

slide16

Mixing induced CP asymmetries

- B  BKs0  (B-factories)

S = - (2+O(s))sin(2)ms/mb + (possible contribution from bsg) = - 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.

slide17

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

b d k mm decay

b

s

Bd→ K*mmdecay

In 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

slide20

Kreuger, Matias hep-ph/0502060

Prospects for Forward-Backward asymmetry measurements

(see M. John talk)

rare decays b s mm for lhcb prospects 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
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:

slide25

LHC Prospects

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)

slide26

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 Bsll
  • exclusive decays (K*, , …)
  • Measurement of BR(B s,d  ) down to SM predictions
  • Search for lepton flavor violation