Searches for New Physics in Charm and Beauty sector at the Tevatron
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Luciano Ristori(Fermilab, INFN-Pisa)
Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
Flavor Physics at the Tevatron
• Tevatron was shut down for good on Sep 30, 2011
• CDF and D0 each have about 10 fb-1 of data on tape
• They were designed for high PT physics. And...• High-rate of all species of heavy flavors: actually higher than “B
factories”• Excellent mass resolution• Precision vertex reconstruction capabilities• Powerful trigger on displaced vertices• Forward-Backward symmetric detectors and CP-symmetric initial
state imply equal number of particles and antiparticles in the acceptance
• Good competitors to the B factories
2Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
Searches for New Physics in Charm and Beauty sector at the Tevatron • This talk is focused on recent Tevatron results in the flavor sector that are
believed to be particularly sensitive to departure from the Standard Model
• New results since last year:
• CP violation in charmless B decays• b →s µ+µ– decays• Branching fraction of Bs→µ+µ– • CP violation in Bd and Bs semi-leptonic decays
• All done with full data set (~10/fb)
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http://www-cdf.fnal.gov/physics/new/bottom/bottom.htmlhttp://www-d0.fnal.gov/Run2Physics/WWW/results/b.htm
Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
CP Asymmetries in Charmless b-hadron Decays
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Correction cf derived from D0 → K+ π – (symmetric production)
First observation of Bs → K-π+ and Bs → K+K -, first evidence of Bs → π+π -
Flavor specific decays (b-flavor from final state charge)Count events and correct for detector-induced charged asymmetries
large Bs and Λb samples unique to the Tevatron until
the turn-on of LHC
Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
CP Asymmetries in Charmless b-hadron Decays
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1.Displaced vertex trigger 2.Reconstruct B-like two-pronged vertices 3.Build invariant mass, assuming ππ hypothesis4.All individual modes overlap in a single broad peak
Analysis Strategy
]2c [GeV/-/+/m5.0 5.2 5.4 5.6 5.8
2 cC
andi
date
s pe
r 10
MeV
/
500
1000
1500
2000
2500
]2c [GeV/-/+/m5.0 5.2 5.4 5.6 5.8
2 cC
andi
date
s pe
r 10
MeV
/
500
1000
1500
2000
2500-1 = 9.30 fbL dt0CDF Run II Preliminary
data
total-/+ KA0B-K+ KA0
sB-/+/ A0B+/
- KA0sB
- pKA0bR
-/ pA0bR
-K+ KA0B-/+/ A0
sB
Multibody B decays
Combinatorial bkg
]2c [GeV/-/+/m5.0 5.2 5.4 5.6 5.8
2 cC
andi
date
s pe
r 10
MeV
/
1
10
210
310
410-/+ KA0B-K+ KA0
sB-/+/ A0B-K+ KA0B
+/- KA0sB
- pKA0bR
-/ pA0bR
-/+/ A0sB
Multibody B decaysCombinatorial bkg
datatotal
]2c [GeV/-/+/m5.0 5.2 5.4 5.6 5.8
2 cC
andi
date
s pe
r 10
MeV
/
1
10
210
310
410
-1 = 9.30 fbL dt0CDF Run II Preliminary
Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
Particle ID with dE/dx and Kinematics
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• Multi-dimensional unbinned likelihood fit to extract yields of each decay mode and its charge conjugate
• Use kinematic variables and particle ID
Particle species separation through kinematics and dE/dx
Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
Correction of detector-induced charge asymmetries
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• We are looking for small effects• Need to correct for small detector asymmetries• π+ vs π- and K+ vs K-
• Millions of D0 to K-π+ and c.c.• Asymmetry corrections of order ~1%
Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
CP Asymmetries in Charmless b-hadron Decays
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precision measurement of b-baryon asymmetries still unique to CDF
Fit results ACP
Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
http://www-cdf.fnal.gov/physics/new/bottom/120628.blessed-Bhh9fb/cdf10726_acp_bhh_9fb_public.pdf
b→s µ+µ- decays
• Flavor Changing Neutral Currents
• Yet another golden probe
• Look for new physics in the distributions of kinematic variables
• Total/differential BR, isospin asymmetry, forward backward asymmetry...
9Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
b→s µ+µ- decays
10Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
Differential BR in b→s µ+µ- decays
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Consistent with SM
Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
Isospin asymmetry in b→s µ+µ- decays
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Consistent with SM within errors
LHCb observes a 3 sigma effect in the highest q2 bin
=
Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
CDF
LHCb 3 sigma discrepancy from SMarXiv:1205.3422
http://www-cdf.fnal.gov/physics/new/bottom/120628.blessed-b2smumu_96/public_b2smumu.pdf
Asymmetries in b→s µ+µ- decays
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Forward-backward asymmetry K* polarization
SM
http://www-cdf.fnal.gov/physics/new/bottom/120628.blessed-b2smumu_96/public_b2smumu.pdf
Also consistent with SM
Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
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Branching fraction of Bs→µ+µ–
• Flavor Changing Neutral Current restricted• Helicity suppressed• BR(B0s→μ+μ− ) ~ 3 x10-9
• Can be significantly enhanced by New Physics
Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
Branching fraction of Bs→µ+µ–
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• Blinded analysis•Dimuon mass range of 4.0 – 7.0 GeV•Blinded from 4.9 – 5.8 GeV
•Expected•SM Signal: 1.23 ± 0.13•Background: 4.3 ± 1.6•Limit: BR(Bs→µ+µ-) = 23x10-9
• Observed 3 events setting a 95% C.L. limit on the branching fraction of
• Normalization mode• B± →J/ΨK± with J/Ψ→µ+µ-
• BDT Multivariate technique• Use data sidebands as background for training
http://arxiv.org/abs/1301.4507Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
Submitted to Phys. Rev. D
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Bs→µ+µ– results
Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
CP violation in Bd and Bs semileptonic decays
17Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
Courtesy of Mark Williams, HCP 2012
CP violation in Bd and Bs semileptonic decays
18Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
Courtesy of Mark Williams, HCP 2012
CP violation in Bd and Bs semileptonic decays
19Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
Courtesy of Mark Williams, HCP 2012
CP violation in Bd and Bs semileptonic decays
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Final result:
consistent with standard model
Phys. Rev. D 86, 072009 (2012)
Phys. Rev. Lett. 110, 011801 (2013)
Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
CP violation in Bd and Bs semileptonic decays
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new results consistent with standard model, also consistent with previous results
overall combination still ~ 3 sigma away from SM
Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
Phys. Rev. D 86, 072009 (2012)
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Conclusions• The Tevatron legacy
The experiments at the Tevatron have shown that precision measurements in flavor physics at a hadron collider are possible and can be complementary and competitive to similar studies at dedicated facilities (B-factories)
• Data taking has ended but analysis continues• More interesting results in flavor physics will be
coming from dear old Tevatron
Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
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THE END
Les Rencontres de Physique de la Vallée d'Aoste - La Thuile - Feb 27 2013 - Luciano Ristori
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