B ATLAS

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?????? B-??????? ?? ????????? ATLAS

• ?.?.???????
• (? ??????? ??
• B-??????)
• http//nuclphys.npi.msu.su/b/index.html
• 18.04.2005

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??????????? LHC

• LHC Large Hadron Collider ??????? ????????
  ????????? ???????? ? ????????? ????? ? CERN?
  pp-???????????? (14 ???).
• ??????????? ?????? ?????? ????? 2007 ?.
• ?????? ?????????
• ATLAS, CMS ??? ?????? ?????? ??????,
  ?????????????? ? ?????? ?????, ? ??? ?????
  ???????????? ??????? b-???????
• LHCb ????????????? ??? B-??????
• ALICE ??? ???????????? ??????? ???.

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• ?? ???????????????? ?? ?????? ??????
• ?-???????? ?? ????????? ATLAS ??????
• ??????, ??? ?????? ??? ??????? ?????????
• ??????? ? ?????? ??????.
• ??????? ????? ?????, ??? ????????????
• CMS ?, ????????, LHCb ????? ?? ?????
• ???????? ????????? ?? ?????? ??????
• ????????

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Introduction - I

• Physics b ? d, s transitions (FCNC) are
  forbidden at the tree level in SM and occur at
  the lowest order through one-loop-diagrams
  penguin and box.
• Main points for study
• a) The good test of SM and its possible
  extensions
• - SUSY, Two Higgs-doublet, LR, Extra
  Dimensions
• b) Information of the long-distance QCD effects
• c) Determination of the Vtdand Vts
• d) Some of rare decays as BG to other rare
  decays
• (for example B0d ? p0 µ µ- as BG to B0s
  ?µ µ- ? ).

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Introduction - II
Branching Ratios Hierarchi in SM Br(B0d ?µ
µ- ) a few 10-10 Br(B0d ?µ µ- ? )
a few 10-10 Br(B0s ?µ µ- ) a few
10-9 Br(B0s ?µ µ- ? ) a few 10-8
Br(B0d ? p0 µ µ- ) a few 10-8 Br(B0d ? ?0
µ µ- ) a few 10-7 Br(B0d ? K µ µ-)
(4.8 1.2) 10-7 (BaBar, Belle, 02) Br(B0s ?
f µ µ- ) a few 10-6 Br(B0d ? K µ µ-)
(1.17 0.33) 10-6 (BaBar, Belle, 03) Br(B0d
? K?) (4.3 0.4) 10-5 (CLEO, 93)
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Which new measurements can LHC make comparing
with B-factories?

• a) The rare decays of B0s meson (B0s?f? ,
  B0s?f µ µ- , B0s ?µ µ- ? and B0s ?µ µ-) and ?b
  - baryon
• b) Differencial distributions for rare
  semileptonic B-meson decays (dimuon-mass spectra,
  forward-backward asymmetries) very sensitive to
  the SM extensions
• c) Branching fractions of rare muonic and rare
  radiative muonic B-meson decays good
  sensitivity to the SM extensions.

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The basic theoretical description -I

• Effective Hamiltonian for b ? d,s transition
• Heff (b ? q) GFVtqVtb? Ci(µ) Oi (µ),
• includes the lowest EW-contributions and
  perturbative
• QCD corrections for Wilson coefficients Ci(µ) .
• µ - scale parameter 5 GeV separates SD
  (perturba-
• tive) and LD (nonperturbative) contributions of
  the
• strong interactions.
• SM NLO A.Buras, M.Munz, PRD52, p.182, 1995
• SM NNLO C.Bobeth et al., JHEP 0404, 071, 2004
• MSSM NNLO C.Bobeth et al., hep-ph/0409293.

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The basic theoretical description -II
Oi (µ) set of the basic operators (specific for
each model SM, MSSM, LR and
others) LD (nonperturbative) contribution of
the strong inte- ractions are contained in the
hadronic matrix elements and are described in
the terms of relativistic invariant function -
transition formfactors.
Need the nonperturbative methods (SR, QM,
Lat).
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The accuracy of calculations

• Stability of the Wilson coefficients to the
  choice of
• mt and µ mb /2, 2mb
• SM NLO approximately 15
• SM NNLO approximately 6 - 7
• MSSM NNLO 30 depends from the
• 
  parameters set.
• Accuracy of the nonperturbative calculations
• depends on a method, but its not less, than 15
  .
• For SM calculations NLO, for MSSM NNLO.

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Simulations of rare B-decays for ATLAS detector
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B0d,s ?µµ- decays in ATLAS

• Points for study in ATLAS
• Branching ratio - sensitive to the SUSY .
• Simulations
• Full Inner detector simulation and reconstruction
  at low and nominal LHC luminosity
• 1) for TDR layout signal background (ATLAS
  TDR 15, Vol.II, 1999)
• 2) for Initial layout only signal
  (ATL-COM-PHYS-2003-003 ).
• 3) signal background in DC2.
• Results
• Using SM teoretical predictions Br(B0d,?µµ- )
  1.510-10 and Br(B0d,?µµ- ) 3.510-9
• we obtaned the following sensitivities for ATLAS
• After 3 year LHC work at L1033 cm-2s-1 (30
  fb-1) will be expected
• B0d 4 signal ev., B0s 27
  signal ev., 93 BG ev. common to both
• After 1 year LHC work at L1034 cm-2s-1 (100
  fb-1) will be expected
• B0d 14 signal ev., B0s 92
  signal ev., 660 BG ev. common to both
• We expect the 31010 sensitivities at CL 95 for
  rare leptonic decays.

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B0d?K(892)µµ- decay at ATLAS

• Points for study in ATLAS
• Branching ratio - sensitive to the SUSY
• Differencial distributions (dimuon-mass spectra,
  AFB) very good
• sensitivity to the
  SUSY.
• Simulations
• Full ATLAS Inner detector simulation and
  reconstruction at low
• luminosity (ATLAS TDR 15, Vol.II, 1999) using
  theoretical matrix
• element from paper D.Melikhov, N.Nikitin,
  S.Simula, PRD57, 6814, 1998.
• Results of simulation
• After 3 year LHC work at L1033 cm-2s-1 (30
  fb-1) will be expected
• 2000 signal events at
  290 BG events

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Radiative penguins in ATLAS
Points for study in ATLAS Branching for Bsf g,
polarization measurements and CP-violation
effects.
Preliminary results Non-optimized offline cuts,
resolution (gt100 MeV/c2) could be improved.
Using DC1 simulation tools estimations including
trigger and off-line selection cuts for 1year
LHC work at L21033cm2s-1 (20fb-1)
Bsf g 3200 signal ev., S/vBG gt 7
BdK0 g 8500 signal ev., S/vBG gt 5. B?K0p0 BG
rejection under investigation combining p0/ ?
rejection cuts, kinematics and angle between B0
and K at Krest frame cuts.
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Baryonic rare decay of ?b? ? µ µ-
Points for study in ATLAS Branching ratio -
sensitive to the SUSY FB asymmetry - very
sensitive to the SUSY . Generation
procedure EvtGen used to generate events using
amplitudes from works (C-H.Chen, C.Q.Geng, PRD64,
074001, 2001 ) and (T.M.Aliev et.al. , NPB649, p.
168-188 , 2003). Results of DC1-simulation At
Br(?b? ? (p p-) µ µ- ) 210-6 after 1 year LHC
work at L21033 cm-2s-1 (20 fb-1) will be
expected 1800 events of the decay ?b? ? (p p-)
µ µ- .
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B0d ? p0 µ µ- as BG to B0d,s ?µµ-? and B0d,s
?µµ- decays

• ?(µ) lt 2.5, pT(µ) gt 6 GeV, p0 ? ? ? , pT(p0) lt
  4GeV
• The decay B0d ?p0 µ µ- are essential background
  for the decay
• B0d,s ?µ µ- (?) at the particle level
  simulation.

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SUSY in rare B-decays at ATLAS detector
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SUSY main motivations for study in rare B-decays

• I) Many kinds of heavy (m gt 1 TeV) SUSY
  particles.
• II) Only lightest of these particles can be
  detected on LHC.
• III) Other SUSY-particles give the tiny
  contributions as
• virtual particles in SM processes.To find
  the information
• on such particles it is necessary to
  choose the decays
• a) where SM contributions are suppressed
  as much as
• possible
• b) QCD nonperturbative corrections well
  known
• c) branchings can be measured in ATLAS.
• Rare B0d,s and ?b decays are IDEAL CHOICE for
  that!

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MSSM for B0d,s?µµ- decays and ATLAS sensitivity

• C.Bobeth et al., PRD66, 074021, (2002)
• The B0d,s?µµ- barnchings as functions of charge
• Higgs boson mass MH for two choice the tan ß.

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MSSM in B ?K(892) µµ- decay and ATLAS precision

Sensitivity of AFB to the choice of the Wilson
coefficients in one MSSM scenario P.Cho,
M.Misiak, D.Wyller, PRD54, p.3329, 1996.
Three intervals for variable q2 /M2B. If in the
first interval the negative average asymmetry
will be measured, it will be convincing
demonstration of a SM exten- sions reality.
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