Abstract
Abstract: The production of beauty and charm quarks in ep interactions has been studied with the ZEUS detector at HERA for exchanged four-momentum squared 5 < Q2< 1000 GeV2 using an integrated luminosity of 354 pb−1. The beauty and charm content in events with at least one jet have been extracted using the invariant mass of charged tracks associated with secondary vertices and the decay-length significance of these vertices. Differential cross sections as a function of Q2, Bjorken x, jet trans- verse energy and pseudorapidity were measured and compared with next-to-leading-order QCD calculations. The beauty and charm contributions to the proton structure functions were extracted from the double-differential cross section as a function of x and Q2. The running beauty-quark mass, mb at the scale mb, was determined from a QCD fit at next-to-leading order to HERA data for the first time and found to be mb(mb) = 4.07 ± 0.14 (fit)− 0.07+ 0.01(mod.)− 0.00+ 0.05(param.)− 0.05+ 0.08(theo.) GeV.
Highlights
We extend the Standard Model with an EW fermion triplet, stable thanks to one of the accidental symmetries already present in the theory
On top of being a potential Dark Matter candidate, additional motivations for this new state are the stability of the vacuum, the fact it does not introduce a large fine-tuning in the Higgs mass, and that it helps with gauge coupling unification
The reach of the other channels is found to extend up to ∼ 1.3 (1.7) TeV for 3 (30) ab−1 of integrated luminosity, provided systematics are well under control. This model constitutes a benchmark of a typical weakly interacting massive particle (WIMP) Dark Matter candidate, and its phenomenology reproduces that of various models of Supersymmetry featuring a pure Wino as the lightest sparticle
Summary
The difference Mχ± − Mχ0 at the two-loop level is 164 ÷ 165 MeV (stable to the level of 1 MeV for Mχ0 1 TeV) [20] This minimalistic picture is directly inspired by the Minimal Dark Matter model [21, 22], which had already considered the phenomenology of EW multiplet as DM candidates. This minimal model can be seen as a benchmark of the typical thermal-relic WIMP Dark Matter candidate, as we already mentioned It is a prototype of more complicated models, and it can reproduce their low energy phenomenology to a remarkable accuracy. As remarked in [20], the first operator that can induce a further splitting arises at dimension 7
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
