Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May, 2012 1 1. Introduction 2. B hh CP...
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Transcript of Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May, 2012 1 1. Introduction 2. B hh CP...
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 1
1. Introduction2. B hh CP violation asymmetries 3. EW gauge boson production4. New b,c spectroscopy and exclusive dimuons5. Some B rare decays and Majorana neutrinos
LHCb RESULTS
54 institutions, 15 countries
3 Spanish universities among them :
Main LHCb highlights by Guy WilkinsonBSM with LHCb tomorrow
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 2
The LHCb Apparatus
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 3
The LHCb Trigger + Data acquisition
4
High efficieny (<90%)& good performance
2011 7.0 TeV 2011 7.0 TeV (1 fb(1 fb-1-1 recorded) recorded)
2010 (37 pb-1 recorded)
LHCb integrated luminosity
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 5
CP-VIOLATIONIN B hh DECAYS
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 6
CP violation , the challenge
Noninvariance of fundamental forces under the combined action of charge conjugation (C) and parity (P) transformations is well established in the K0 and B0 meson systems 1
Recent results from LHCb also provided evidence of CP violation in the decays of D0 meson: R. Aaij et al. (LHCb Collaboration) Phys. Rev. Lett. 108, 111602 (2012)
Yet LHCb has found CP violation in the only neutral heavy meson that remains, the Bs : R. Aaij et al. (LHCb Collaboration) Phys. Rev. Lett. 108, 201601 , published 16 May 2012
1 J. H. Christenson, J.W. Cronin, V. L. Fitch, and R. Turlay, Phys. Rev. Lett. 13, 138 (1964). B. Aubert et al. (BABAR Collaboration), Phys. Rev. Lett. 87, 091801 (2001). K. Abe et al. (Belle Collaboration), Phys. Rev. Lett. 87, 091802 (2001).
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 7
CP violation , the challenge
All current experimental measurements of CP violation in the quark flavor sector are generally well described by the Kobayashi-Maskawa mechanism which is embedded in the framework of the Standard Model (SM) 1 .
However, it is believed that the size of CP violation in the SM is not sufficient to account for the asymmetry between matter and antimatter in the Universe 2 . Hence, additional sources of CP violation are being searched for as manifestations of physics beyond the SM.
1 N. Cabibbo, Phys. Rev. Lett. 10, 531 (1963). M. Kobayashi and T. Maskawa, Prog. Theor. Phys. 49, 652 (1973). 2 W.-S. Hou, Chin. J. Phys. (Taipei) 47, 134 (2009), http://psroc.phys.ntu.edu.tw/cjp/download.php?type=full&vol=47#=2&page=134.
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 8
Charmless Two-Body Decays Bs,d →h+ h-
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 9
Bs,d →h+ h- direct CP violation
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 10
Direct CP-asymmetry in Bs → K+ π-
Phys. Rev. Lett. 108, 201601
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 11
Annihilation Diagrams
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 12
Effective Bs →K+ K- Lifetime
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 13
Time Dependent B0 → K+ π- Fit
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Time Dependent CP Violation in B0 → π+π-
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Time Dependent CP Violation in Bs →K+ K-
t0 = 0.95 ps
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 16
Summary on CPV asymmetries in Bs,d →h+ h-
(see Paula Alvarez’s talk tomorrow)
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 17
Measurement of the Ds+ Ds
- production asymmetry in 7 TeV pp collisions
LHCb has determined the overall production asymmetry of Ds mesons
produced directly in pp collisions in the rapidity region 2.0 < < 4.5 and pT > 2 GeV :
0.10)%0.220.33()σ(D)σ(D
)σ(D)σ(DA
ss
ssP
Which is consistent with theoretical expectations 1 and , provides significant constraints on models of Ds
production, and it is a key input for CP violation measurements.
LHCb-PAPER-2012-009 May 4, 2012
M. Chaichian and A. Fridman Phys. Lett. B298 (1993) 218.E. Norrbin and R. Vogt arXiv:hep-ph/0003056 E. Norrbin and T. Sjostrand Eur. Phys. J. C17 (2000) 137.
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 18
Ds+ Ds
- production asymmetry results
Subtle sources of production asymmetries :- only c can form a charmed baryon- non-independent fragmentation process- even interference with S-waves - are they reduced at central rapidities?
LHCb has reconstructed 771.031 Ds mesons with 1 fb-1 , using both magnet polarities,
and determined the +/ - detection asymmetries in (p,pT) to 1% .
Key idea: use the ratio of partial/full reconstructed D* S
D0 decays .
D0 K-++(-)3-momentum determined fromslow pion S
reconstruction
D*
RS
WS
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 19
Ds+ Ds
- production asymmetry
Then use reconstructed Ds
K+ K- decays to measure theproduction asymmetry. Note no significant CP violation in decay is expected 1
being a Cabibbo favoured mode.
1 Y. Grossman, A. L. Kagan, and Y. Nir, Phys. Rev. D75 (2007) 036008 S. Bergmann and Y. Nir JHEP 09 (1999) 031.
Overall production asymmetry AP = (-0.33 0.22 (stat.) 0.10 (syst.)) %
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W,Z BOSON PRODUCTION WITH LHCb
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 21
Electroweak boson production at LHCb
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EW boson production and PDFs
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EW boson production ratios
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W l signal
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Results Z production
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W production and W/Z ratios
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Results W+- asymmetry
Differential W+- asymmetry consistent with NNLO predictions
Lepton pseudorapidity
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Combined Electroweak Physics
b AND c SPECTROSCOPY
29Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012
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B** spectroscopy
Mesons consisting of LIGHT / HEAVY quarks are an interesting laboratory to study QCD, just as the hydrogen atom was to understand QED.
The states with L=0 and spin-parity 0- (B) and 1- (B*) are well established. But precision spectroscopy of orbitally excited B states is still undone. Properties predicted by HQET (Heavy Quark Effective Field Theory).
,
,
100-200 MeV/c2 expected widths
Subject of LHCb study
Key idea : the spin of the heavy quark and the total spinJl of the light degrees of freedom are separately conserved.
31
B** spectroscopy
Phys. Rev. Lett. 102 (2009) 102003.
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012
CDF 2009
First precision measurement by CDF II
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B** spectroscopy
How LHCb reconstructs B** states
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B** spectroscopy
B**0 B+- B**+ B0+
First observationFirst observationLHCb-CONF-2011-53LHCb preliminary 2011 data, 336 pb-1
Fit: signal 2 BW’s for B* 2 with fixed mass difference 45.8 MeV for M(B*)-M(B) (PDG)1 BW for B1. Fix yield ratio of two B* 2 transitions to be 0.930.18 [Phys. Rev. D64 (2001) 114004.]Fix B1/B2 width to be 0.90.2 [Phys. Rev. D53(1996) 231.] (B2
*) = 20.6 2.0 MeV/c2 Background: WS component + 2 broad gaussians representing B0* and B’1 states
B1 B2* B2
*+ B1+
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 34
B** spectroscopy
BS2* BS1
(BS1) = 0.65 0.07 MeV/c2
(BS2*) = 1.85 0.13 MeV/c2
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 35
B** spectroscopy
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Charmonium-like exotics
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Charmonium-like exotics
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Charmonium-like exotics
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Charmonium-like exotics
nb
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 40
Charmonium-like exotics
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Charmonium-like exotics
Physical Review D 85,091103(R) (2012)
No confirmation of narrow J/ state X(4140) ; no evidence for X(4274)
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Bc and b-baryons
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Bc+ meson mass measurement
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Bc+ cross-section
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Bc+ J/ + - + mode
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Bc+ J/ + - + results
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Bc+ J/ + - + production
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Masses of b , b
LHCb-CONF-2011-060
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Masses of b , b
LHCb-CONF-2011-060
b[dsb] , b [ssb]
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Production of Λ0b Λ+
c- + -
Phys. Rev. D84 (2011) 092001. Phys. Rev. D84 (2011) 092001.
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Λ0b and b in D0pK- mode : preliminary
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Observation of excited Λb0 baryons
First observation by LHCb, significance of 4.9 and 10.1
Appreciable mismatch with respect to existing relativistic quarks models, reasonable agreement with large Nc (spin-averaged) approaches.arXiv:1205.3452v1 [hep-ex] 15 May 2012
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 53
Measurements of b-hadron masses
LHCb has achieved world-best measurements of theB-meson and baryon masses in exclusive modes.The momentum is calibrated with J/ +- decays and verified to a relative precisionof 2 10-4 using other 2-body decays.
CDFCDFCDFCDF
BaBar
Mesons and baryons are colourlessobjects formed by quarks and gluons andbound by strong interaction. Masses can becompared with lattice QCD calculations.
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 54
Summary on b,c spectroscopy at LHCb
B**sector LHCb has access to the poorly explored B**sector, and will improve the knowledge of their properties and decays X,Y,Z states First studies of X(3872) and X(4140) demonstrate potential of LHCb to explore the exotic meson sector. Future results on larger data sets. Bc studies at LHCb Mass and cross section measured using 2010 data First observation of Bc
+ J/ + - + (6.8 ) b baryon studies at LHCb Mass and lifetime of Λb
0 using 2010 data world best measurement by LHCb Masses of b , b measured using 2011 data world best measurement by LHCb Productions of Λb
0 measured with various decay modes first observation of Λ0
b D0pK- (6.8 ) and b D0pK- (2.6)
FORWARD DIMUONS
55Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012
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Central Exclusive Dimuon Production No backward tracks, two forward tracks, no identified photon
c0,c1,
c2
J/ (2s)
pb925112474)4.5η(2σJ/
pb1571067)/cGeV2.5m,4.5η(2σ 2μμpppp
Consistent with 42 1 pb (QED)
Relative proportions c0 , c1, c2 very sensitive to models that can potentially explore gluon x 2 10 -6
0.03 0.20 σ/σ ψ(2s)J/
Previous result by CDF: PRL 102 (2009) 242001
SOME RARE b-DECAYS AND SEARCH FOR MAJORANA NEUTRINOS
57Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012
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Search for B+ ++-
5.2 significance for B+ ++- signal yield 25.3-6.4 +6.7 events, 1 fb-1 integrated luminosity
Normalisation to B+ J/ K+
Branching ratio = (2.4 0.6 (stat.) 0.20 (syst.) ) 10-8
in good agreement with SM expectation 1 (1.96 0.21) 10-8
1 S. Hai-Zhen, L. Lin-Xia, and L. Gong-Ru, New Physics Effects on rare decays B+ ++- and B+ ++- in a top quark two-higgs-doublet model, Communications in Theoretical Physics 50 (2008) 696.
Best published limit : < 6.9 10-8 at 90% CL by Belle Collaboration Phys. Rev. D78 (2008) 011101
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 59
Search for Bs (B0) + - + -
Non-resonant Bs 4µ decay highly suppressed in SM 1 , BR < 10-10. But may be enhanced by NP due to FCNC mediated by new particles decaying into µ+ µ- pairs 2
1 D. Melikhov and N. Nikitin, PRD 70, 114028 (2004) 2 S. Demodov and D. Gorbunov Flavor violating processes with sgoldstino pair production, arXiv:1112.5230.
Seven Bs J/ events observed in the resonant window (estimated BR (2.3 0.9) 10-8 ))
Using the full 1 fb-1 2011 data sample, in the non-resonant window after unblinding, one Bs µ+ µ- µ+ µ- event and no B0 µ+ µ- µ+ µ- evts are observed.
95% CL upper limits: B (Bs µ+ µ- µ+ µ- ) < 1.3 10-8
and B (B0 µ+ µ- µ+ µ- ) < 5.4 10-9
Expected backgrounds are :0.38-0.17 +0.23 (0.30-0.20 +0.22 ) for Bs (B0 )
LHCb-CONF-2012-010
Bs
B0 non-resonant window
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Search for Majorana neutrinos at LHCb
arXiv:1201.5600v2 [hep-ex] 23 Mar 2012b
du
c
¯
W-
W-
N
+
-
a)
b)
c)
Virtual Majorana neutrino
Resonant neutrino production
Also resonant production
“Searches for Majorana neutrinos in B- decays” (The LHCb Collaboration)
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 61
Majorana neutrinos B- D+(*)- -
B- D+-- B- D*+--
No signal evidence, background from side bands
BR (B- D+--) < 6.9 10-7 95% CLBR (B- D*+--) < 2.4 10-6 95% CL
1 More stringent than previous Belle result , Phys. Rev. D84 (2011) 071106
1
a)
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012 62
Majorana neutrinos B- +- -
and B- Ds+- -
No signal seen above backgrounds: Neutrino on-shell masses (m4) have been searched for :
m4m4
b)
63
Mass and lifetime acceptance for on-shell Majorana Neutrinos
B- +-- B- Ds+-- B- D0 +--
Neutrino mass acceptance
Our search has ignored thus far the possibility of a finite neutrino lifetime. All sensitivity is lost for lifetimes longer than 10-10s to 10-11s.
B- +--
Mass dependent upper limits on BR
(of course this does not apply for virtual Majoranas)
Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012
b)
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Summary of Majorana neutrinos
Using B- +-- , neutrino mass dependent upper limits were established on the couplings |V4| of a heavy Majorana N to a muon and virtual W using matrix elements from [1]. A model dependent calculation [2] was used for B- D0 +-- , but the mode +-- is more sensitive. For the B- D+(*)- - , upper limits on the coupling cannot be extracted until there is theoretical calculation of hadronic form factor (as there is for 0 decay) .
[1] A. Atre, T. Han, S. Pascoli, and B. Zhang, JHEP 05 (2009) 030, arXiv:0901.3589. [2] D. Delepine, G. Lopez Castro, and N. Quintero, Phys. Rev. D84 (2011) 096011, arXiv:1108.6009.
b)
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Conclusion
LHCb has shown powerful performance as a forward detector in pp collisions at s = 7 TeV for precision b and c physics, with very good mass and proper time resolution, and excellent K/ separation : observation of asymmetries in forward production of EW bosons first observation of new resonances and decay modes great potential for exploring rare decays, including lepton flavor violation CP-violation has been observed for the first time in D0 and Bs mesons, and a wide range of measurements is forseen, with potential new physics discovery, both in CP-violation and very rare decays (see G. Wilkinson’s talk tomorrow)
BACKUP
66Bernardo Adeva, USC Winter Meeting IMFP-2012 Benasque 30 May , 2012
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Lifetime distributions B0 and Bs
B0 → π+π-
Bs →K+ K-
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Charm spectroscopy
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Charm spectroscopy
Feed-down states DJ →D*(D*→D,D0)
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Charm spectroscopy
Feed-down states DsJ →D*K(D*→D,D0)
mmmmmmmmmmmmmmm
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Lifetime of Λb preliminary
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Mass of Λb
Phys. Lett. B 708 (2012) 241.
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Phys. Lett. B 708 (2012) 241.
Phys. Rev. D85 (2012) 032008.
Production of Λ0b : semi-leptonic decays