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Exotic Dijets Research and ATLAS Experiment Responsibilities

This research summary highlights the work of Professor Michael Shupe and the Exotic Dijets group at the University of Arizona on the ATLAS experiment at CERN, including the search for new phenomena, FCal and radiation shielding design, radiation fluences and doses, authorships and editorial board service, and postdoctoral appointees and their activities.

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Exotic Dijets Research and ATLAS Experiment Responsibilities

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  1. Summary of Research and Responsibilities on ATLAS Experiment at CERN: Professor Michael ShupeUniversity of ArizonaJuly, 2015 • Exotic Dijets group, search for new phenomena. • ATLAS FCal and radiation shielding design. • ATLAS radiation fluences and doses, 1992 to the present, including Phase 1 and 2 designs. • Authorships, and service on Editorial Boards. • Postdoctoral appointees and their activities. • Focus on quark/lepton compositeness.

  2. Search for New Phenomena in Dijet Angular Distributions in Proton-Proton Collisions at sqrt(s) = 8 TeV, Measured with the ATLAS Detector: Phys. Rev. Lett. 114, 221802. The hypothesis here is that if quarks are composite, the constituents (preons) would lead to quark contact interactions (qq  qq). Events would appear above the QCD background at high dijet mass, and at large scattering angles. In the Chi variable shown here, these signal events would appear at low Chi. No significant signal is observed. In this analysis, mass scales below 12.0 TeV have been excluded. (96 X Higgs mass.)

  3. Search for New Phenomena in the Dijet Mass Distribution in ATLAS 2012 Data using pp Collisions at sqrt(s) = 8 TeV: Phys. Rev. D. 91, 052007. Again, assuming that quarks are composite, it is possible that they could be excited, appearing as short-lived resonances (q*) at higher masses. Using the dijet mass spectrum from data, the analysis looks for significant excesses (bumps) above the QCD background. For this model, q* masses below 4.09 TeV have been excluded.

  4. Many Hypotheses Have Been Excluded to High Masses. Exotic Dijet Results

  5. ATLAS’ Adoption of Arizona’s FCal and Shielding Design Tracking Calorimeters Muon: Air Core Toroids Integrated Forward Calorimeters ($16M) Massive Forward Radiation Shield (~700 Metric Tonnes) Arizona was the only U.S. group to make a major change in the ATLAS design! We conceived the integrated FCal and the radiation shield design, adopted by ATLAS in June,1994.

  6. Arizona conceived, engineered, and supervised the Integrated Forward Calorimeter project for ATLAS. Our research group constructed the FCal EM module in a clean room in the basement of the Physics building. FCal hadronic modules were constructed in Canada, by Canadian and Russian collaborators. Our FCal concept included design of the massive forward radiation shield. Background studies are ongoing, for Phase II (below).

  7. NIEL Damage [1 MeV eq n/cm^2/Yr] – Cu LAr MiniFCal, Phase II Option ATLAS 2012 Cu LAr MiniFCal SW> SW> ID ID ID FCal FCal The LAr MiniFCal would increase the NIEL dose slightly at the inner radii of the EMEC and HEC, but it has negligible effect on the ID, the SW, and the HEC electronics.

  8. Deposited Energy [GeV/cm^3/s] – LAr MiniFCal Phase II Option HEC <SW ID FCal

  9. M. Shupe, Exotic Dijets Authorships, 2010-2013 CI - quark contact ints, (qqqq) q* - excited quark, (q*qg) s8 - scalar color octet W’ - heavy W boson SR - string resonance axig - axigluon QBH – quantum black hole Univ Toronto: AW (Andreas Warburton) and PS (Pekka Sinervo)

  10. Growth of the Exotic Dijets Group, 2010-Present List Institutions in the ATLAS Exotic Dijets Group in 2010: Univ Arizona, Univ Cambridge, CERN, Charles Univ, Univ Chicago, Univ Glasgow, Lund Univ, McGill Univ, Univ Oxford, Univ Tokyo, Univ Toronto, Univ Wisconsin.  23 Group Members Present List Institutions in the ATLAS Exotic Dijets Group: Univ Arizona, Univ Buenos Aires, Cal State Fresno, UC Irvine, Univ Chicago, CERN, Czech Tech Univ, Univ Geneva, Harvard Univ, Kirchhoff Inst, Lund Univ, Univ Mainz, Univ Oxford, Univ Paris-Diderot (LPNHE), INFN Roma, Sapienza Roma, Simon Fraser Univ, Shandong Univ, Tel-Aviv Univ, Tsinghua Univ.  45 Group Members Much of the attraction to the Exotic Dijets Group is that the search and discovery analyses are very generic, and cover a large mass range. Also, beyond the Higgs, no new particles have appeared at low masses, and some popular theories are being excluded within the expected mass range.  In the current Group, there are more native English speakers, and capable authors, than in the past. So the Convenors have assigned other group members to be primary authors. (I am in complete agreement with this decision.)

  11. Arizona Postdocs in the ATLAS Exotic Dijets Group Frederik Ruehr: Frederik joined the Arizona EEPP Group in Feb. 2010. He received his Ph.D. from the University of Heidelberg in 2009, and was already working in the ATLAS Exotic Dijets Group. In mid-2010, Ruehr was appointed to be the Convenor of the ATLAS Jet+X subgroup, which included both Standard Model physics and the search for new physics – in dijet distributions, in inclusive jet spectra, and in a number of other Jet+X channels. In 2013, he joined the ATLAS group at the University of Freiburg, and is now working on other ATLAS analyses. VenkateshVeeraraghavan:Venkatesh joined our Arizona Group in May, 2014. He received his Ph.D. from Florida State University, and his thesis (and the following publication) were based on a search for slow heavy charge particles in CMS. Since arrival in Arizona, he has been working with me and with Peter Loch on jet and dijet issues. His ATLAS qualification project focused on MET coding that would be compatible with Athena and AOD analyses. Venkatesh is now at CERN, and is pursuing several ideas for augmenting the existing dijet analyses. These will be described in his presentation.

  12. Composite models date from the late 1970’s through the early 1980’s. M. Shupe published this model in 1979. It is based on spin ½ preon doublets, one with charge e/3, and the other, neutral. Haim Harari was working on a similar model at the same time, so this is known as the Harari-Shupe model. It also appears as a homework problem in Griffiths’ Intro. to Elementary Particles.

  13. - In 2012, Don Lincoln, who works at Fermilab near Chicago, and is a popularizer of physics, wrote a Scientific American cover article that describes my composite model for quarks and leptons.

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