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Physics Signal Observation at ATLAS

#G-1995


Investigation of the possibility of the new physics signals observation at ATLAS experiment

Tech Area / Field

  • PHY-PFA/Particles, Fields and Accelerator Physics/Physics

Status
3 Approved without Funding

Registration date
11.01.2012

Leading Institute
Tbilisi State University, Georgia, Tbilisi

Supporting institutes

  • B.I. Stepanov Institute of Physics, Belarus, Minsk

Collaborators

  • CERN, Switzerland, Geneva\nArgonne National Laboratory, USA, IL, Argonne\nMax-Planck-Institut für Physik, Germany, Munich\nStockholm University, Sweden, Stockholm

Project summary

The goal of the proposed project is the participation in the researches within the physics program of the ATLAS (A Toroidal LHC ApparatuS) experiment. The ATLAS is general-purpose proton-proton experiment, operated at the Large Hadron Collider (LHC) at European Organization for Nuclear Research (CERN, Geneva, Switzerland). The LHC started its operation and collided protons at √s = 7 TeV in 30-th of March of 2010 with a bunch spacing of 50 ns. Physics running started at L = 1.9·1027 cm−2 s−1 and then during 2010-2011 years increased in several steps to a target of L = 2 · 1032 cm−2 s−1. Subsequent running will be at or near √s = 14 TeV with 25 ns bunch spacing and luminosity of L = 1034 cm−2 s−1 after 2014 for several years. ATLAS is the largest collider experiment ever built. Its size is determined by the extent of its muon system which uses 20 m diameter air-core toroids and endcap planes separated by 46 m.
The research goals and tasks of the proposed project are:
1. The Tile Calorimeter sub-detector behavior and stability analysis by use of DCS data.
2. Development, validation and then apply a search for flavor changing neutral current (FCNC) top quark decays in the initial ATLAS data samples from 2010-2012, giving sensitivity to FCNC significantly beyond what has been achieved by previous experiments.
3. Investigation of flavour changing neutral current inspired B-meson, heavy quarks and lepton rare decays in frame of large extra dimension models. We are going to recognize beyond standard model effects’ signatures for such models, which could be discovered at ATLAS experiment.
4. Implementation and development of new Network and Computing technologies (installation, configuration and support of ATLAS Tier3S center) in Georgia.
5. Investigation of a magnetic monopole with ATLAS data.
6. Study of the Bose-Einstein correlations in pp-interactions in new energy region 7 – 14 TeV with the research goals to measure the radius and chaoticity of like charged hadrons correlation in dependence of charged hadrons multiplicity, including new high multiplicity region, transverse momentum of charged hadrons, transverse moment of like charged pars of hadrons using ATLAS experiment data collected with minimum-bias and high multiplicity triggers.
7. Investigation of energy correlators and their ratios, and chemical potential in pp-integrations in new energy region 7 – 14 TeV with ATLAS detector with the research goal to discovery of thermalization phenomena at high multiplicity of charged hadrons.
The ATLAS has a great physics discovery potential. To perform the mentioned above researches successfully, ATLAS needs to have very good electromagnetic and hadronic calorimeters for the identification and energy measurement of photons, electrons, charged hadrons and hadronic jets, and also for measurement of missing transverse energy. The main task of the Tile Hadronic Calorimeter Detector Control System (TileCal DCS) is to enable the coherent and safe operation of the detector. All actions initiated by the operator and all errors, warnings, and alarms concerning the hardware of the detector are handled by the DCS. The DCS has to continuously monitor all system parameters, provide warnings and alarms concerning the hardware of the detector. Because calorimeter will be working for long period during data taking (9-10 months per each year) it is very important to control permanently all main system, accumulate necessary information for fixation of failed component and provide stable functionality of detector elements in future.
Top quark physics, which is one of the main issues in ATLAS physics program, is one of the research issues of the proposed project. Top-antitop quark pairs will be produced at LHC predominantly via QCD processes (gluon-fusion and quark-antiquark annihilation) with large cross section of 872.8pb. This large cross section means that LHC will be a prolific source of top quarks and produce about 9 million t¯t events per year (at “low” luminosity, 1033 cm−2 s−1), a real “top factory”. Such large event samples will permit precision measurements of the top-quark parameters. FCNC interactions of the top quark with a light quark q = u, c through gauge (Z, γ, g) or Higgs (H0) bosons do not appear in the Standard Model (SM) at tree level and are strongly suppressed in the SM due to the Glashow-Iliopoulos-Maiani (GIM) mechanism. For the top quark within the framework of the SM, these contributions limit the FCNC decay branching ratios to the gauge bosons, BR (t→qX, X = Z, γ, g), to below 10-10, well out of reach of sensitivity of the Tevatron or the LHC. Any observation of such FCNC decays would therefore signal physics beyond the standard model. The participants of the project L.Chikovani and T.Djobava together with the physicists participating in ATLAS Collaboration studied in 1995-2007 years the ATLAS experiment sensitivity to top quark FCNC rare decays t → Zu(c), t → u(c) and t → gu(c) in tt- pair production based on the signal and background processes generation and simulation (Eur. Phys. J. C52, p.999, 2007). Different types of analyses (the cut-based analysis method and the likelihood analysis method) were used for the estimation of the Branching ratios of these decays at 5σ level and at 95% C.L. for luminosities L= 10, 100 fb-1
Part of this project will focus on FCNC manifestations in quarks and leptons rare decays as probes for physics beyond the SM (BSMP). In particular, it will be explored possible signatures of BSMP scenarios involving Large Extra Dimensions (LED). Furthermore the realization that leptogenesis might be the primary effect underlying the observed baryon number in the Universe makes searches for CP violation in the lepton sector more mandatory than ever. The proposed research aims at making specific suggestions for observable signatures of such BSMP scenarios that could be searched at ATLAS experiment at CERN. As a central element it will be analyzed FCNC??transitions with respect to their widths, the photon polarizations and CP asymmetries. It will be investigated FCNC processes also in the lepton sector. The analysis will be based on the operator product expansion and heavy quark theory, where appropriate. It will be compared LED predictions with those obtained within the SM and its SUSY extensions, both the SM results and results which were obtained by different authors and by participants of the project A. Liparteliani and G.Devidze in frames of various extensions of the SM. The goal in this direction is to identify those transitions that carry the greatest promise of differentiating between TeV scale BSMP from SUSY and LED.
The implementation of above mentioned tasks needs development of new Network and Computing technologies (installation, configuration and support of ATLAS Tier3S center) in Tbilisi State University (Georgia).
Another goal of the project is the investigation of the possible existence (or nonexistence) of magnetic charge in the nature. The elaboration of the new proposals for experimental search for magnetic monopoles in the framework of the project ATLAS and also development of the self-consistent phenomenological approach to description of the possible effects of monopole connections. The strongest argument in favor of the existence of the magnetic monopole is the quantization of electric charge. Secondly, the monopole's existence leads to the symmetrization of Maxwell's equations in classical electrodynamics. The introduction of magnetic charge and magnetic current density would make the equations invariant under a global duality transformation. And, finally, magnetic monopoles are predicted from field theories which unify the fundamental forces. While most of the theoretical models tend to favor GUT monopoles with masses M~1016-1017 GeV and cannot discovered on the modern accelerators. But in some Grand Unified models lower mass monopoles, with masses of order a few TeV are allowed. These circumstances have stimulated the experimental search for magnetic monopoles at accelerators. Till now no experimental evidence of the monopole existence has been found despite the experimental search at HERA, LEP2 and Tevatron. Therefore LHC should obtain own experimental data in respect of the monopole existence. Project participant (Yu.Kurochkin, Y.Kulchitsky, I.Satsunkevich, Dz.Shoukovy, P.Tsiareshka) are the authors of the series of the works which devoted to problems of the magnetic charges.
One of the important ATLAS task is study of the Bose-Einstein correlations in pp-interactions in new energy region 7 – 14 TeV with the research goals to measure the radius and chaoticity of like charged hadrons correlation in dependence of charged hadrons multiplicity, including new very high multiplicity region, transverse momentum of charged hadrons, transverse momentum of like charged pars. The study of BEC in pp-collisions at 0.9 and in new energy region 7 - 14 TeV collected by the ATLAS experiment using the minimum-bias and high multiplicity triggers will be done. We will have investigated the Bose-Einstein correlations using two particle C(Q) function. Different reference samples, needed for its construction, will be used: the N+-(Q) one, obtained as a 4-momentum difference between positive and negative tracks taken from the same event, and the N++--em(Q) one, obtained from the same-signed pairs combination of tracks from different events as well as the opposite hemisphere and rotated track reference distributions. Two parameterizations of the source emission probability will be used. The first one has the Gaussian shape, and the second one, introduced to obtain a better fit of the experimental data, has the exponential form after Fourier transform. The values for the radius R of the two-pion emitter and the coherence factor λ, or chaoticity factor, of the BEC effect will be measured. We will use a particle identification dE/dx from the pixel detector as well as the information from TRT explicitly identify kaons and pions and in such a way to retrieve the Bose-Einstein effect more properly. The participants of the project Y.Kulchitsky, S.Harkusha and P.Tsiareshka together with the physicists participating in ATLAS Collaboration studied the experiment sensitivity to study Bose-Einstein correlations.
The ATLAS detector have very good potential for investigation of two and three hadrons energy correlators and their ratio, and chemical potential in pp-integrations in new energy region 7 – 14 TeV with the research goal to find manifestation of thermalization phenomena. The idea of this investigation is the discovery of new physics thermalization phenomena in the region of very high multiplicity of charged hadrons. This thermalization phenomena must manifested as itself as hadrons energy distribution symmetry reinforcement in a final state. The investigation of correlation effects in the region of very high multiplicity of charged hadrons in pp-interaction is actual task of modern high energy physics. The main aim of our study is measurement of two and tree particles energy correlators and their ratio in dependence of charged hadrons multiplicity and identification of for witch multiplicity the correlators ratio will be smaller than unit (that will be reflection of manifestation of certain intermediate object like “gluon condensate”) and for with multiplicity the correlators ratio will be more smaller than unit, that will be reflection of asymptotic condition of system. The participants of the project Y.Kulchitsky, Yu.Kurochkin, S.Harkusha and P.Tsiareshka together with the physicists participating in ATLAS Collaboration studied the ATLAS experiment sensitivity to energy correlators at high multiplicity of charged hadrons.
The group of project participants consists from experienced, highly qualified scientists as well as from young, beginner scientists and students. Project Main Staff – L.Chikovani, G.Devidze, T.Djobava, J. Khubua, Y. Kulchitsky, Yu.Kurochkin, A.Liparteliani, I.Minashvili, M.Mosidze, I.Satsunkevich, Dz.Shoukovy are participating very actively in preparation and solving of theoretical and experimental researches within the ATLAS Experiment program since 1994. The young participants of the project will acquire the experience, knowledge and increase their professional level. The proposed activities in this project all fit nicely within other international and national scientific, educational and technological activities in Georgia and Belarus. The proposed project will definitely contribute in the raise/improve of the scientific and technological base of our countries.


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