Prospects of search for New Physics
in B decays at LHC Andrey Golutvin
ITEP / Moscow
In CP - violation
In rare decays

Slide2:

In CP-violation

Slide3:

Accuracy of sides is limited by theory:
Extraction of |Vub|
Lattice calculation of Accuracy of angles
is limited by experiment:
= ± 13°
b = ± 1.5°
= ± 25° Mean values of angles and sides of UT are
entirely consistent with SM predictions 3

Slide4:

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 Standard strategy to search for New Physics

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 (245)° 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:

b q u, c, t u, c, t q b W+ W− V*ib Viq Viq V*ib trees d-/s- penguins d-/s- boxes Compare experimental observables measured in different topologies: Complementary Strategy

Slide8:

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

Slide9:

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

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)) andlt; 30° (d-penguin)
- (2(NP)) ~8° (2.6 hint) (s-penguin)
- ((NP)) not measured yet (s-penguin)
PS (NP) = (NP)

Slide11:

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) LHCb (see M.John talk)

Slide12:

In Rare Decays

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 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)

Slide16:

Polarized b decays:
b (1115)
(1115) p violates pariry
Assuming b polarization andgt; 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/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 )

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 !!!)
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, 2002
D.Atwood,T.Gershon,M.Hazumi,A.Soni hep-ph/0701021 v 1
V. Shevchenko paper in preparation

Bd → K*mm decay:

Bd → K*mm decay Bd m m g 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 andlt; 0.5 Branching ratio:(1.22+0.38 -0.32) 10-6 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

Slide19:

18

Slide20:

Kreuger, Matias hep-ph/0502060 Prospects for Forward-Backward asymmetry measurements
(see M. John talk)

Slide21:

LHCb prospects:

LHCb prospects

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

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):
andlt; 7 x 10 -8
Expected final limit at 95% CL (8 fb-1):
andlt; 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 andlt; m1/2 (gaugino mass) andlt; 650 GeV 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: 10-7
10-8
10-9

Slide25:

LHC Prospects

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 Bsll
exclusive decays (K*, , …)
Measurement of BR(B s,d ) down to SM predictions
Search for lepton flavor violation

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