Unequal strengths of boundary localised terms lead to non-conservation of the Kaluza-Klein (KK) parity in the 4 + 1 Universal Extra Dimensional model. Consequently the first excited KK-partners of Standard Model particles are not stable by any symmetry. In this article using the latest 13 TeV Large Hadron Collider (LHC) results, we revisit the resonant production of first KK-excitations of the neutral gauge bosons ($G^1$, $B^1\ \textrm{and} \ W_3^1$) and their subsequent decay. {\it Specifically $G^1$ (first KK-excitation of gluon) decays to $t\bar{t}$ pair and $B^1/W_3^1$ (first KK-excitation of electroweak gauge bosons) decay to $\ell^{+}\ell^{-} (\ell \equiv e, μ)$ pair}. We find the exclusion limits of model parameters obtained at 95\% C.L. from the non-observation of these channels have been shifted towards the lower side of the parameter space compared to our previous analysis at 8 TeV.
We present an updated analysis of the rare decay $K_{L}\toπ^{0}μ^{+}μ^{-}$ within the Standard Model. In particular, we present the first complete calculation of the two-photon CP-conserving amplitude within Chiral Perturbation Theory, at the lowest non-trivial order. Our results confirm previous findings that the CP-conserving contribution to the decay rate cannot be neglected. By means of an explicit two-loop calculation, we show that this contribution can be estimated with sufficient accuracy compared to the CP-violating terms. We predict $\cB(K_L\toπ^0μ^+μ^-)_{\rm SM}=(1.5\pm0.3)\times10^{…
More than two decades ago, we studied heavy-flavor-conserving weak decays of heavy baryons within the framework that incorporates both heavy-quark and chiral symmetries. In view of the first observation of $Ξ_b^-\toΛ_b^0π^-$ by LHCb recently, we have reexamined these decays and presented updated predictions. The predicted rates for $Ξ_b^-\toΛ_b^0π^-$ in the MIT bag and diquark models are consistent with experiment. The major theoretical uncertainty stems from the evaluation of baryon matrix elements. The branching fraction of $Ξ_c\toΛ_cπ$ is predicted to be of order $10^{-4}$. It is suppressed…
The decay K_L -> pi0 e+ e- is being searched for as a signal of direct Delta S = 1 CP violation. We provide a thorough updating of the analysis of the three components of the decay: 1) Direct CP violation, 2) CP violation through the mass matrix and 3) CP-conserving (two-photon) contributions. First the chiral calculation of the K_S -> pi0 e+ e- rate, due to Ecker, Pich and de Rafael (EPR), is updated to include recent results on the nonleptonic amplitude. Then we systematically explore the uncertainties in this method. These appear to be so large that they will obscure the direct CP violation…
We discuss the phenomenology of charged Higgs bosons in the MSSM with minimal flavor violation. In addition to the constrained MSSM (CMSSM) with universal soft supersymmetry breaking mass parameters at the GUT scale, we explore non-universal Higgs mass models (NUHM) where this universality condition is relaxed. To identify the allowed parameter space regions, we apply constraints from direct searches, low energy observables, and cosmology. We find that values of the charged Higgs mass as low as $m_{H^+}\simeq~135$ GeV can be accommodated in the NUHM models, but that several flavor physics obse…
The full ATLAS Run 2 data set with time-integrated luminosity of 139 fb$^{-1}$ in the diboson and dilepton channels is used to probe benchmark models with extended gauge sectors: the $E_6$-motivated Grand Unification models, the left-right symmetric $LR$ and the sequential standard model (EGM). These all predict neutral $Z'$ vector bosons, decaying into lepton pairs, $\ell\ell$, or into electroweak gauge boson pairs $WW$, where one $W$ in turn decays semileptonically. 95% C.L. exclusion limits on the $Z'$ resonance production cross section times branching ratio to electroweak gauge boson pairs…
We present new global fits of the cMSSM, including LHC 1/fb integrated luminosity SUSY exclusion limits, recent LHC 5/fb constraints on the mass of the Higgs boson and XENON100 direct detection data. Our analysis fully takes into account astrophysical and hadronic uncertainties that enter the analysis when translating direct detection limits into constraints on the cMSSM parameter space. We provide results for both a Bayesian and a Frequentist statistical analysis. We find that LHC 2011 constraints in combination with XENON100 data can rule out a significant portion of the cMSSM parameter spac…
We revisit the limit on very light axion-like particles (ALPs) from the absence of gamma rays coincidental with the neutrino burst from SN1987A. We use updated supernova simulations, modern models for the magnetic field inside the Galaxy, and a Primakoff cross section which takes into account proton-degeneracy and mass-reduction effects. We finally give an updated exclusion plot for the electromagnetic coupling of sub-eV ALPs, comparing our new bound with other limits as well as with future ALP searches.
We explore the constraints on the parameter space of a Randall-Sundrum warped geometry scenario, where a radion field arises out of the attempt to stabilise the radius of the extra compact spacelike dimension, using the most recent data from higgs searches at the Large Hadron Collider (LHC) and the Tevatron. We calculate contributions from both the scalar mass eigenstates arising from radion-higgs kinetic mixing in all important search channels. The most important channel to be affected is the decay via WW*, where no invariant mass peak can discern the two distinct physical states. Improving u…
Rare kaon decays are an important testing ground of the electroweak flavor theory: They can provide new signals of CP-violating phenomena. The interplay of long-distance QCD effects in strangeness-changing transitions can be analyzed with Chiral Perturbation Theory techniques. In particular, two rare kaon decays are analyzed: The first decay, K_L -> pi0 e+e-, is being searched for as a signal of direct Delta S = 1 CP violation. We provide a thorough updating of the analysis of the three components of the decay: 1) Direct CP violation, 2) CP violation through the mass matrix and 3) CP-conservin…
We describe recent developments of the public computer code HiggsBounds. In particular, these include the incorporation of LHC Higgs search results from Run 2 at a center-of-mass energy of 13 TeV, and an updated and extended framework for the theoretical input that accounts for improved Higgs cross section and branching ratio predictions and new search channels. We furthermore discuss an improved method used in HiggsBounds to approximately reconstruct the exclusion likelihood for LHC searches for non-standard Higgs bosons decaying to $ττ$ final states. We describe in detail the new and updated…
The theoretical calculation of pseudo-scalar leptonic decay widths into an invisible ALP, $M \to \ell\, ν_\ell\, a$, is reviewed. Assuming generic flavour-conserving ALP couplings to SM fermions and a generic ALP mass, $m_a$, the latest experimental results for pseudo-scalar leptonic decays are used to provide updated bounds on the ALP-fermion Lagrangian sector. Constrains on the ALP-quark couplings obtained from these channels are not yet competitive with the ones derived from FCNC processes, like $M\to P\,a$ decays. These leptonic decays can, however, provide the most stringent model-indepen…
We consider flavor-changing decays of neutral Higgs bosons in the context of CP-conserving BGL model - a variant of 2HDM Type 3 model suggested by Branco, Grimus and Lavoura - in which tree-level FCNC couplings are suppressed by elements of known fermion mixing matrices. The relevant regions of parameter space compatible with experimental restrictions on the SM Higgs properties are studied. We also include current bounds on h-> mu tau into consideration. In addition, different FCNC decay modes are analyzed for heavier Higgs states (H/A) and conservative estimates for Br(A/H->mu tau) are provid…
Direct detection experiments have set increasingly stringent limits on the cross section for spin-independent dark matter-nucleon interactions. In obtaining such limits, experiments primarily assume the standard halo model (SHM) as the distribution of dark matter in our Milky Way. Three astrophysical parameters are required to define the SHM: the local dark matter escape velocity, the local dark matter density and the circular velocity of the sun around the center of the galaxy. This paper studies the effect of the uncertainties in these three astrophysical parameters on the XENON1T exclusion …
Improved Big Bang Nucleosynthesis constraints on decaying massive relics
Deutsches Elektronen-Synchrotron DESY（德国电子同步加速器）；Dipartimento di Fisica, Sapienza Università di Roma & Sezione INFN Roma1（罗马第一大学物理系与INFN罗马一分部）；Service de Physique Théorique, Université Libre de Bruxelles（布鲁塞尔自由大学理论物理服务处）；CP3-Origins, University of Southern Denmark（南丹麦大学CP3起源中心）
The model independent bounds on new neutral vector resonances masses, couplings and widths presented at arxiv:1112.0316 are updated with an integrated luminosity of L=4.7 fb^-1 from ATLAS and L=4.6 fb^-1 from CMS. These exclusion limits correspond to the most stringent existing bounds on the production of new neutral spin-1 resonances that decay to electroweak gauge boson pairs and that are associated to the electroweak symmetry breaking sector in several extensions of the Standard Model.
In five-dimensional universal extra-dimensional models compactified on an $S^1/Z_2$ orbifold four-dimensional kinetic terms are allowed at the two fixed points. If these terms are unequal then Kaluza-Klein (KK) parity is broken. Within such a framework we consider resonant production of the n = 1 KK-gluon at the Large Hadron Collider and its subsequent decay to $t\bar{t}$, where both production and decay are KK-parity non-conserving. We use, for the first time, the exclusion data for a $t\bar{t}$ resonance obtained by the ATLAS collaboration to limit the mass ranges of quark and gluon excitati…
We consider the natural supersymmetry scenario in the framework of the R-parity conserving minimal supersymmetric standard model (called natural MSSM) and examine the observability of stop pair production at the LHC. We first scan the parameters of this scenario under various experimental constraints, including the SM-like Higgs boson mass, the indirect limits from precision electroweak data and B-decays. Then in the allowed parameter space we study the stop pair production at the LHC followed by the stop decay into a top quark plus a lightest neutralino or into a bottom quark plus a chargino.…
We discuss resonant squark production at the LHC via baryonic $R$-parity violating interactions. The cross section easily exceeds pair-production and a new set of signatures can be used to probe squarks, particularly stops. These include dijet resonances, same-sign top quarks and four-jet resonances with large $b$-jet multiplicities, as well as the possibility of displaced neutralino decays. We use publicly available searches at $\sqrt{s}=8$ TeV and first results from collisions at $\sqrt{s}=13$ TeV to set upper limits on $R$-parity violating couplings, with particular focus on simplified mode…
We compute the 3-loop O(αα_s) correction to the Higgs boson production cross section arising from light quarks using an effective theory approach. Our calculation probes the factorization of QCD and electroweak perturbative corrections to this process. We combine our results with the best current estimates for contributions from top and bottom quarks to derive an updated theoretical prediction for the Higgs boson production cross section in gluon fusion. With the use of the MSTW 2008 parton distribution functions that include the newest experimental data, our study results in cross sections ap…
Rare charm decays offer the unique possibility to explore flavour-changing neutral-currents in the up-sector within the Standard Model and beyond. Due to the lack of effective methods to reliably describe its low energy dynamics, rare charm decays have been considered as less promising for long. However, this lack does not exclude the possibility to perform promising searches for New Physics per se, but a different philosophy of work is required. Exact or approximate symmetries of the Standard Model allow to construct clean null-test observables, yielding an excellent road to the discovery of …
In a recent paper, we updated the theoretical predictions for the production cross sections of the Standard Model Higgs boson at the Tevatron and estimated the various uncertainties affecting these predictions. We found that there is a large theoretical uncertainty, of order 40%, on the cross section for the main production channel, gluon-gluon fusion into a Higgs boson. Since then, a note from the Higgs working groups of the CDF and D0 collaborations criticizing our modeling of the $gg\to H$ cross section has appeared. In this addendum, we answer to this criticism point by point and, in parti…
We present an analysis on the production of two same-sign lepton pairs at the LHC, mediated by bileptons in the $SU(3)_c\times SU(3)_L\times U(1)_X$ theory, the so-called 331 model. Compared to other 331 scenarios, in this model the embedding of the hypercharge is obtained with the addition of 3 exotic quarks and doubly-charged vector gauge bosons with lepton numbers $\pm 2$ in the spectrum ($Y^{\pm\pm}$), which can mediate the production of four-lepton final states. Furthermore, a complete description of the model requires the introduction of a Higgs scalar sector, which is a sextet of $SU(3)…
Experimental search potential for sbottom via $\tildeχ^{\pm}_1$ decays at the LHC Run-3 and HL-LHC, in final states with same-sign leptons and multiple jets
The existence of the tiny neutrino mass and the flavor mixing can be naturally explained by type-I Seesaw model which is probably the simplest extension of the Standard Model (SM) using Majorana type SM gauge singlet heavy Right Handed Neutrinos (RHNs). If the RHNs are around the Electroweak(EW)-scale having sizable mixings with the SM light neutrinos, they can be produced at the high energy colliders such as Large Hadron Collider (LHC) and future $100$ TeV proton-proton (pp) collider through the characteristic signatures with same sign di-lepton introducing lepton number violations(LNV). On t…
Naturalness arguments applied to simple supersymmetric (SUSY) theories require a set of light higgsinos with mass $\sim |μ|$ not too far from $m_h$. These models have an inverted electroweakino spectrum with $|μ| \ll M_2$ which leads to a rather clean, hadronically quiet, same-sign diboson (SSdB) signature at hadron colliders arising from neutral-plus-charged wino pair production. We improve and expand our earlier studies of this signature for discovering SUSY in natural SUSY models by (i) including backgrounds which were not previously considered and which turn out to be significant, (ii) dev…
