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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: - PowerPoint PPT Presentation
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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