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Title: Energy spectra of massive two-body decay products and mass measurement

Here, we have recently established a new method for measuring the mass of unstable particles produced at hadron colliders based on the analysis of the energy distribution of a massless product from their two-body decays. The central ingredient of our proposal is the remarkable result that, for an unpolarized decaying particle, the location of the peak in the energy distribution of the observed decay product is identical to the (fixed) value of the energy that this particle would have in the rest-frame of the decaying particle, which, in turn, is a simple function of the involved masses. In addition, we utilized the property that this energy distribution is symmetric around the location of peak when energy is plotted on a logarithmic scale. The general strategy was demonstrated in several specific cases, including both beyond the standard model particles, as well as for the top quark. In the present work, we generalize this method to the case of a massive decay product from a two-body decay; this procedure is far from trivial because (in general) both the above-mentioned properties are no longer valid. Nonetheless, we propose a suitably modified parametrization of the energy distribution that was used successfully for the masslessmore » case, which can deal with the massive case as well. We test this parametrization on concrete examples of energy spectra of Z bosons from the decay of a heavier supersymmetric partner of top quark (stop) into a Z boson and a lighter stop. After establishing the accuracy of this parametrization, we study a realistic application for the same process, but now including dominant backgrounds and using foreseeable statistics at LHC14, in order to determine the performance of this method for an actual mass measurement. The upshot of our present and previous work is that, in spite of energy being a Lorentz-variant quantity, its distribution emerges as a powerful tool for mass measurement at hadron colliders.« less
 [1] ;  [2] ;  [1] ;  [3]
  1. Univ. of Maryland, College Park, MD (United States)
  2. Univ. of Maryland, College Park, MD (United States); European Organization for Nuclear Research (CERN), Geneva (Switzerland)
  3. Univ. of Maryland, College Park, MD (United States); Univ. of Florida, Gainesville, FL (United States)
Publication Date:
OSTI Identifier:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Journal of High Energy Physics (Online)
Additional Journal Information:
Journal Name: Journal of High Energy Physics (Online); Journal Volume: 2016; Journal Issue: 4; Journal ID: ISSN 1029-8479
Springer Berlin
Research Org:
Univ. of Florida, Gainesville, FL (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS Hadron-Hadron scattering (experiments); Beyond Standard Model