High Energy Physics Phenomenology

In a previous work we developed a search strategy for staus produced by the decay of the heavy CP-even Higgs bosonHwithin the context of the largetanβregime of the minimal supersymmetric standard model (MSSM) in an scenario of large stau mixing. Here we study the performance of such search strategy by confronting it with the complementary mixing pattern in which decays of both the CP-even and CP-odd heavy Higgs bosons contribute to the production of??1????2+c.cpairs. Again, we focus on final states with two opposite-sign tau leptons and large missing transverse energy. We find that our proposed search strategy, although optimized for the large stau mixing scenario, is still quite sensitive to the complementary mixing pattern. For instance, with a total integrated luminosity of only 100 fb??we are able to exclude heavy Higgs masses above 850 GeV for average stau masses higher than 290 GeV. We also extend the results reported in the preceding work for the large mixing scenario by including now the exclusion limits at 100 fb??and the prospects both for exclusion and discovery in a potential high luminosity phase of the LHC (1000 fb??). Finally, we discuss the possibility to distinguish the two mixing scenarios when they share the same relevant mass spectrum and both reach the discovery level with our search strategy.

Displaced vertices at colliders, arising from the production and decay of long-lived particles, probe dark matter candidates produced via freeze-in. If one assumes a standard cosmological history, these decays happen inside the detector only if the dark matter is very light because of the relic density constraint. Here, we argue how displaced events could very well point to freeze-in within a non-standard early universe history. Focusing on the cosmology of inflationary reheating, we explore the interplay between the reheating temperature and collider signatures for minimal freeze-in scenarios. Observing displaced events at the LHC would allow to set an upper bound on the reheating temperature and, in general, to gather indirect information on the early history of the universe.

We investigateS=??production from the?p??K+Xreactions within the effective Lagrangian approach. The?p??K+??and?p??K+???preactions are considered to find the lightestS=??system, which isH-dibaryon. We assume that theH(2250)?�Λ�?, andH(2270)?????pdecays with the intrinsic decay width of 1 MeV. According to our calculations, the total cross-sections for?p??K+??and?p??K+???preactions were found to be of the order of a fewμb in the?beam momentum range of up to 5 GeV/c. Furthermore, the direct access of information regarding the interference patterns between theH-dibaryon and non-resonant contributions was demonstrated.

Motivated by the LHCb-group discovery of exotic hadrons in the range (6.2??6.9) GeV, we present new results for the masses and couplings of0++fully heavy(Q¯Q)(QQ¯)molecules and(QQ)(QQ¯¯¯¯¯¯¯¯)tetraquaks states from relativistic QCD Laplace Sum Rule (LSR) within stability criteria where Next-to-Leading Order (NLO) Factorized (F) Perturbative (PT) corrections is included. As the Operator Product Expansion (OPE) usually converges ford�???, we evaluated the QCD spectral functions at Lowest Order (LO) of PT QCD and up to??G3??. We also emphasize the importance of PT radiative corrections for heavy quark sum rules in order to justify the use of the running heavy quark mass value in the analysis. We compare our predictions in Table 3 with the ones from ratio of Moments (MOM). The broad structure arround (6.2??6.9) GeV can be described by theη¯¯¯cηc,J/?¯¯¯¯¯¯¯¯¯J/?and?¯¯¯c1?c1molecules or/andS¯¯¯cSc,A¯¯¯¯cAcandV¯¯¯¯cVctetraquarks lowest mass ground states. The narrow structure at (6.8??6.9) GeV if it is a0++state can be a?¯¯¯c0?c0molecules or/and its analogueP¯¯¯¯cPctetraquark. The?¯¯¯c1?c1predicted mass is found to be below the?c1?c1threshold while for the beauty states, all of the estimated masses are above theηbηbandΥ(1S)Υ(1S)threshold.

We calculate theO(??H??H??2/?4)corrections to LEP electroweak precision data using the geometric formulation of the Standard Model Effective Field Theory (SMEFT). We report our results in simple-to-use interpolation tables that allow the interpretation of this data set to dimension eight for the first time. We demonstrate the impact of these previously unknown terms in the case of a general analysis in the SMEFT, and also in the cases of two distinct models matched to dimension eight. Neglecting such dimension-eight corrections to LEP observables introduces a theoretical error in SMEFT studies. We report some preliminary studies defining such a theory error, explicitly demonstrating the effect of previously unknown dimension-eight SMEFT corrections on LEP observables.

We continue our endeavor to investigate lepton number violating (LNV) processes at low energy in the framework of effective field theory (EFT). In this work we study the LNV tau decays?+??????P+iP+j, where??e, μandP+i,jare the lowest-lying charged pseudoscalars?+, K+. We analyze the dominant contributions in a series of EFTs from high to low energy scales, namely, the standard model effective field theory (SMEFT), the low-energy effective field theory (LEFT), and the chiral perturbation theory (?PT). The decay branching ratios are expressed in terms of the Wilson coefficients of dimension-five and -seven operators in SMEFT and hadronic low energy constants. These Wilson coefficients involve the first and second generations of quarks and all generations of leptons and thus cannot be explored in low energy processes such as nuclear neutrinoless double decay or LNV kaon decays. Unfortunately, the current experimental upper limits on the branching ratios are too weak to set useful constraints on those coefficients. Or, if we assume the new physics scale is larger than 1 TeV, the branching ratios are well below the current experimental bounds. We also estimate hadronic uncertainties incurred in applying?PT to?decays by computing one-loop chiral logarithms and attempt to improve convergence of chiral perturbation by employing dispersion relations in the short-distance part of the decay amplitudes.

We perform a model-independent analysis of the magnetic and electric dipole moments of the muon and electron. We give expressions for the dipole moments in terms of operator coefficients of the low-energy effective field theory (LEFT) and the Standard Model effective field theory (SMEFT). We use one-loop renormalization group improved perturbation theory, including the one-loop matching from SMEFT onto LEFT, and one-loop lepton matrix elements of the effective-theory operators. Semileptonic four-fermion operators involving light quarks give sizable non-perturbative contributions to the dipole moments, which are included in our analysis. We find that only a very limited set of the SMEFT operators is able to generate the current deviation of the magnetic moment of the muon from its Standard Model expectation.

The photoproduction reaction ofγp??K+?(1405)is investigated based on an effective Lagrangian approach at the tree-level approximation with the purpose of understanding the reaction mechanism and extracting the resonance contents and the associated resonance parameters in this reaction. Apart from thet-channelKandK??exchanges,s-channel nucleon (N) exchange,u-channelΣ,?, and?(1405)exchanges, and generalized contact term, the exchanges of a minimum number ofNresonances in theschannel are taken into account in constructing the reaction amplitudes to describe the experimental data. It is found that by introducing theN(2000)5/2+resonance exchange in theschannel, one can reproduce the most recent differential cross-section data from the CLAS Collaboration quite well. Further analysis shows that the cross sections ofγp??K+?(1405)at high energies are dominated by thet-channelKexchange, while the contributions from thes-channelNandN(2000)5/2+exchanges are rather significant to the cross sections in the near-threshold energy region. Predictions for the beam and target asymmetries forγp??K+?(1405)are given.

The angular-averaged differential cross section (dcs) of the elastic electron proton (ep) scattering, covering Q^2 < 1.0GeV^2, was fitted via a combined modified eq-scatterings where q is a point particle. The modifications represent the cloud-covering effects to q. An energy-decaying ratio (edr) was derived by inspecting the generated dcs ep from the form factor data gathered at Mainz Microtron (A1-Collaboration) and Continuous Electron Beam Accelerator Facility (Jefferson Laboratory) when compared to the dcs eq with modified relativistic recoil factor. The diminishing cloud layer, edr, has a decay rate of -2.8 for the data sets under investigation. The formulated SBM and SEM fitting models use the bare and effective u and d-quark masses, respectively, while SCBM and SCEM integrate other considerations. Three comparison methods were used and all of them favor the models with other additional considerations. SCEM was the most favored model in general.

Black hole superradiance is a powerful tool in the search for ultra-light bosons. Constraints on the existence of such particles have been derived from the observation of highly spinning black holes, absence of continuous gravitational-wave signals, and of the associated stochastic background. However, these constraints are only strictly speaking valid in the limit where the boson's interactions can be neglected. In this work we investigate the extent to which the superradiant growth of an ultra-light dark photon can be quenched via scattering processes with ambient electrons. For dark photon massesmγ????10??7eV, and for reasonable values of the ambient electron number density, we find superradiance can be quenched prior to extracting a significant fraction of the black-hole spin. For sufficiently largemγ??and small electron number densities, the in-medium suppression of the kinetic mixing can be efficiently removed, and quenching occurs for mixings?0?�O(10??); at low masses, however, in-medium effects strongly inhibit otherwise efficient scattering processes from dissipating energy. Intriguingly, this quenching leads to a time- and energy-oscillating electromagnetic signature, with luminosities potentially extending up to??1057erg/s, suggesting that such events should be detectable with existing telescopes. As a byproduct we also show that superradiance cannot be used to constrain a small mass for the Standard Model photon.