pavel krokovny heidelberg university on behalf of lhcb collaboration
DESCRIPTION
Search for New Physics in CP violating measurements at LHCb. Pavel Krokovny Heidelberg University on behalf of LHCb collaboration. Introduction LHCb experiment Physics results b S measurements prospects Conclusion. Why CP violation?. - PowerPoint PPT PresentationTRANSCRIPT
Pavel Krokovny
Heidelberg University
on behalf of LHCb collaboration
• Introduction• LHCb experiment• Physics results
S measurements prospects
• Conclusion
Search for New Physics in CP violating measurements at LHCb
Why CP violation?
• CP violating parameters are well predicted by the Standard Model
• Good sensitivity to New Physics• Huge statistics allows to perform a precise
measurements
LHCb features
• Large bb cross section & acceptance: huge statistics• Efficient trigger: reducing very high background• Excellent vertexing: resolving fast Bs oscillation• Good tracking & PID: signal reconstruction & background
suppression
S measurement in BS mixing
• Bs->J/ is dominated by tree
diagram. (penguin contribution
is in order of 10-3-10-4)
• Interference between direct &
mixing decays gives a CP
violating phase S=M-2D.
• S in SM is small and well
predicted: S=0.03630.017
• Good sensitivity for New
Physics: S=SSM+S
NP
Angular analysis
Flavor tagging• Need to determine BS flavor at production time.
• Two methods: Same Side (Kaon flavor) and Opposite Side (other B flavor)
• Two key parameters: efficiency () and dilution factor D=(1-2)
• Effective tagging power proportional to D2
• OST is calibrated on data using self-tagged B decays: B+D*+, J/K+
• SST calibration: using double tag method
Flavor tagging performance
• Flavor tagger was tuned using 48K B0->D*-+ events
• Then we check performance on 6K B0->D-+ events
• eff(SS+OS) = 4.31.0 %
compatible with MC expectation
• md = 0.4990.0320.003 ps-1
world average: 0.5070.005 ps-1
Mixing in B0D-+
LHCb-Conf 2011-010
BSJ/ signal
LHCb-Conf 2011-006
75728 eventsBs mass
Lifetime
S result
• Feldman-Cousins method used to get CL contours in S- plane
• Statistical errors only (systematic effects found to small in comparison with statistical uncertainty)
LHCb-Conf 2011-006
S prospects
Expectation!
Additional channels for s
• BsJ/ f0
J/ f0 is CP even eigenstate: angular analysis not needed.
Measurement of S to come soon. (error ~1.5 of J/)
First observation!
Phys.Let.B698:115, 2011
measurements
Two set of methods to measure :
• loop diagram: Bhh (possible NP contribution)
• tree diagram: BDK (theoretically clean)
Difference in results will indicate for New Physics.
from Bhh
Large penguins contributions in both decays
Bd/s
/K
/K/K
/K
Bd/s
Method:
Measure time-dependent CP asymmetry for B and BsKK and exploit U-spin flavor symmetry for P/T ratio (R. Fleischer).
Take s, d from J/,J/Ks can resolve
Direct CPV in Bhh
K+- K-+
ACP(BdK)=-0.0880.0110.007 (world average: -0.0980.12)
ACP(BSK)=0.270.080.02 CDF: 0.390.17
K+-K-+
LHCb-Conf-2011-042
37 pb-1
from BDKInterference between tree-level decays; theoretically clean
Parameters: , rB, δ
Three methods for exploiting interference (choice of D0 decay modes):
• Gronau, London, Wyler (GLW): Use CP eigenstates, e.g. D0 h+ h -
• Atwood, Dunietz, Soni (ADS): Use doubly Cabibbo-suppressed decays, e.g. D0 K+π -
• Dalitz plot analysis of 3-body D0 decays, e.g. Ks π+ π-
Vcs* Vub: suppressedFavored: Vcb Vus
*
b
u
s
u u
b
u
cD0
K-
B- B-
u
s
u
c
D0f
Common
final state
K-
iiBKDBA
KDBA eer
0
0
ADS methodD. Atwood, I. Dunietz and A. Soni, PRL 78, 3357 (1997); PRD 63, 036005 (2001)
Enhancement of СР-violation due to use of Cabibbo-suppressed D decays
B–D0K– - color allowed, D0K+π– - doubly Cabibbo-suppressed
B–D0K– - color suppressed, D0K+π– - Cabibbo-allowed
Interfering amplitudes are comparable
coscos2)(
)( 22
fav
supDBDBADS rrrr
KDBBr
KDBBr
R
)()( 00 KDKDrD AA
Measured quantities:
ADSDBADS RrrKDBBrKDBBr
KDBBrKDBBr/sinsin2
)()(
)()(
supsup
supsup
A
ADS analysis at LHCb
4.0 significance
RADS=(1.660.390.24) 10-2
World average: -0.580.21
AADS=-0.390.170.02
World average: 1.60.3 (w/o LHCb)
LHCb-Conf 2011-044
Conclusion
• LHCb shown a good performance in B & charm physics.
• B-factories & Tevatron sensitivity overtaken or matched on many topics using 2010 data only.
• No sign of New Physics yet .• Great potential to search for New Physics in next
years!
Backup
Control Channels
B+ J/ K+
B0 J/ K*0
• Tagging calibration (opposite side)
• Kinematically similar to BsJ/
• Angular acceptance checks: Polarization amplitudes
• Check of tagging performance
J/ amplitudes
LHCb data taking
LHCb collected 37 pb-1 in 2010, and 670 pb-1 in 2011
One day of operation now corresponds to whole 2010 statistics!
B mixing
d b
b d
W
t
t
WBd Bd
Due to the different values of CKM couplings the Bs mixes faster then the Bd
s b
b s
W
t
t
WBs Bs
Bd → Bd
Bd → Bd
Bd mixingBs mixing
Bs → Bs
Bs → Bs
Bs mixing
Both the Bd and Bs mixing have been precisely measured in experiments
5.1 x 1011 Hz 1.8 x 1013 Hz
BS mixing formalism
Additional channels for s
Pure penguin decays
First observation!
LHCb-Conf 2011-019
Br(BsK*K*)=(1.950.470.51 0.29)10-5
Lifetime measurement for BsK+K-
CPV in charm• Indirect CPV: mixing rate of D0D0 and D0D0 differ
• Direct CPV: amplitudes for D0/D0 differ, mixture of mixing and decay diagram.
• The SM predicts very small CPV in charm: O(10-4).
• Can be up to O(10-2) in some NP models.
• Good prospects to search NP in charm!
• Promising modes: CS modes with penguin contribution:
Charge asymmetry in D0h+h-
• Production and soft pion asymmetry cancel in ARAW(f)ARAW(g)
• There is no detection asymmetry in D0h+h-
D0h+h- ACP results
• Fit the mass difference: M(D*)-M(D0)
• Result: ACP(KK)ACP()= (0.280.700.25) %
Belle: (0.860.600.07)%
BaBar: (0.240.62)% naïve difference
CDF: (0.460.33)% w/o systematic
LHCb-Conf 2011-023