Physics with the ATLAS detector on LHC (JINR participation)

1
Physics with the ATLAS detector on LHC (JINR
participation)

• V. Bednyakov, N. Russakovich

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The ATLAS detector
Over the last decade JINR-ATLAS team was deeply
involved in designing, construction, tests and
assembly of major systems of ATLAS Inner
Detector Tile Calorimeter Liquid Argon End Cap
Calorimeter Muon detector Common Items (Toroid
Warm Structure and others)
Participation in the Physics Program was always
considered as the most important target. Till
2003 this work has been performed mainly in
background regime, essentially based on
individual efforts, promoted with limited
resources case-by-case (as well as for software
developments and general computing infrastructure
of ATLAS).
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Workshops on the ATLAS Physics Program

• Early 2004 the JINR-ATLAS team management decided
  to establish a regular framework (series of
  workshops) to promote physics-oriented activities
  at home, aimed to
• Open the door for new ideas (also attract new
  collaborators, interested in future physics at
  LHC)
• Monitoring of ongoing activities and select most
  promising ones to provide the necessary support,
  in particular for visiting conferences and
  dedicated ATLAS meetings
• Enrich home community by involving physicists
  from JINR member countries who have less
  possibilities in computing and networking, to
  make JINR-ATLAS resources and experience widely
  available
• Keep people informed about recent software
  developments and dedicated computing
  infrastructure at JINR.
• Web site http//www.atlas-jinr.ru/

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Higgs boson

• Search for the SM Higgs boson with the ATLAS
  detector (G.Chekov, I.Boiko, K.Nikolaev,
  R.Sadikov)
• The process H?4µ was investigated on the basis of
  the full ATLAS detector simulation. Further
  investigation of the identical muons effect on
  the decay H?4µ was also carried out.

• The proposals were made to study in Dubna the
  ATLAS large-mass Higgs discovery potential by
  means of reactions H?2W?2l?,or H?2W?l?jj
  (Yu.Kulchitsky) and H?2Z?2l?, or H?2Z?lljj
  (V.Vinogradov) on the basis of the already
  simulated ATLAS DC1 and DC2 data. The proposals
  rely on the Higgs boson production via the Vector
  Boson Fusion mechanism (the two accompanying
  forward jets allows very good background
  reduction) and on the maximal Higgs boson decay
  rates into WW- or ZZ-pair at MH400--1000 GeV.
  At the moment the works are still on the step of
  these proposals.

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Quark-gluon structure functions, VHM

• The possibilities of measuring at the LHC
  energies the gluon distributions in the proton by
  means of simultaneous registration of the direct
  photons (or Z-bosons) and jets (so called
  "gamma/Zjet" events) were carried out by
  D.Bandurin and N.Skachkov. The correspondent
  talks are given at the both Workshops. The task
  is under investigation also at the Tevatron
  energies (D0 project).

• Study of Very High Multiplicity Events at LHC
  (J.Budagov, Yu.Kulchitsky, I.Manjavigze,
  A.Sissakian,).

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SANC

• Project SANC (Support of Analytical and Numerical
  Calculations for Experiments at Colliders).
• D.Bardin, L.Kalinovskaya, P.Christova, G.Nanava
  A.Andonov (DLNP, JINR), A.Arbuzov, S.Bondarenko
  (BLTP, JINR).
• The status of HEP (semi-)analytical calculation
  tool for LHC was presented by its leader
  D.Bardin. At the moment this very ambitious and
  quickly progressing project is not yet ready for
  practical investigations of the prospects for
  observation of the physical phenomena at the LHC
  with ATLAS detector. Nevertheless it promises to
  be much more useful for development of the
  JINR-ATLAS physical program right in the near
  future.
• http//brg.jinr.ru/

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Top quark physics

• N.Russakovich, V.Bednyakov, E.Khramov, S.Tokar,
  A.Tonoyan
• Verification of the of the top-quark charge
• With the help of the PYTHIA and ATLFAST
  simulations the prospects for correct
  verification of the statement that the top-quark
  electric charge indeed equals to 2/3 is
  performed on the basis of the lepton-jet top
  decay channels.
• Search for ttbar resonance with ATLAS
• Resonances with several masses are considered
  (500, 1000, 1500 GeV) with PYTHIA 6.203 event
  generator and processed with ATLFAST integrated
  in ATHENA framework.

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Theoretical calculations and estimates

• Evaluation of the next-to-leading order QCD
  corrections to the single top- and top-anti-top
  quarks production together with an estimate of
  the associate top-Higgs production (in
  pp-interactions) were given by A.Akhmedov. Some
  aspects of research of the top- and Higgs boson
  production and the search for the exotic
  phenomena at LHC were discussed by Z.Usubov.
  Theory and phenomenology of the ATLAS physics
  with the Higgs bosons, the extra gauge bosons and
  (very) heavy quarkonia states as well as a theory
  of the multi-particle correlations during
  particle productions were given by G.Kozlov. Just
  an idea about monopole search with the ATLAS
  detector was presented by Yu.Kurochkin (Minsk).
  The diffractive Higgs production and search for
  the virtual electroweak effects with ATLAS were
  discussed by I.Satsunkevich (Minsk). V.Gilevsky
  (Minsk) gave report on general parameterization
  of 4-boson vertex and its importance for the
  collider physics.

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Theoretical calculations and estimates

• P.Starovoitov (Minsk) considered two-photon
  mechanism of Drell-Yan lepton pair production in
  pp-collisions and demonstrated that its
  contribution is not negligible.

• Supersymmetry and Dark Matter search at LHC
  
• ( V.Bednyakov, S.Kovalenko).
• The highest importance of the SUSY search at
  LHC (especially in connection with cosmology and
  astrophysics via famous problem of the Dark
  Matter) needs no any extra arguments
  Unfortunately, till now there is no any
  Dubna-based ATLAS simulation activity in the
  field. The situation will be improved in the
  nearest future.

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Search for gravitons (extra dimensions)

• The possibility of observation of the graviton
  exchange effects on dijet production was studied
  by Z.Usubov on the basis of ATLAS detector
  simulation with PYTHIA and ATLFAST. A sensitivity
  of the LHC to a main parameter of the graviton
  production model is estimated.

• The search for and identification of the direct
  and indirect manifestations of the graviton-like
  Kaluza-Klein states in the lepton-pair production
  at LHC A.Pankov (Gomel). The new Center-edge
  asymmetry was introduced to isolate the spin-2
  graviton contribution. This well developed and
  attractive theoretical proposal now is ready to
  enter the ATLAS-simulation phase.

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Conclusions

• We have more than enough fresh attractive ideas
  which can be and should be incorporated into the
  ATLAS research program.
• Only very few of above proposals have passed a
  way from initial idea to clear experimental
  procedure through simulation, background
  estimates and so on. We have to work intensively
  LHC start up is approaching!
• My proposal to other Dubna-LHC groups (CMS,
  ALICE) and their leaders would be let us arrange
  a common framework joint home workshops on LHC
  physics. Despite of some differences like
  detector particularities and software used we all
  (I believe) could get a lot of benefit from
  mutual discussions.