Abstract

A TeV scale leptoquark (LQ) is one of the promising explanations of the recent anomalies in the semileptonic decays of 퐵 mesons. Among the various LQs, the vector U1 is capable of explaining the anomalies in both 푅퐷(∗) and 푅퐾 (∗) observables. We use the current LHC data to put bounds on the parameter space of U1 relevant for the anomalies. Precise bounds are drawn by recasting the latest 휏휏 and 휇휇 searches by the ATLAS and CMS collaborations. We find that it is imperative to include the resonant production modes for obtaining limits in the low mass regions. For higher mass points, the non-resonant production modes play a dominant role.

Abstract

Extensive searches to probe the particle nature of dark matter (DM) have been going on for some decades now but, so far, no conclusive evidence has been found. Among various options, the Weakly Interacting Massive Particles (WIMP) remains one of the prime possibilities as candidates for DM near the TeV scale. Taking a phenomenological view, such null results may be explained for a generic WIMP in a Higgs-portal scenario if we allow the light-quark Yukawa couplings to assume non-Standard Model (non-SM)-like values. This follows from a cancellation among different terms in the DM-nucleon scattering which can, in turn, lead to a vanishingly small direct-detection cross section. It might also lead to isospin violation in the DM-nucleon scattering. Such non-SM values of light-quark Yukawa couplings may be probed in the high luminosity run of the LHC.

Abstract

Entanglement is a fascinating feature, typical and ubiquitous to the science of quantum information and computation. Over the last few decades, we have seen entanglement, or more precisely bipartite entanglement, playing an unparalleled role in various quantum information-theoretic tasks [1–3]. Multipartite entanglement comes with an even richer structure and a whole new set of features providing information processing advantages in quantum communication, simulation, or metrology. It is therefore essential to construct methods to identify genuinely multipartite entangled states [4–6]. However, detecting entanglement of an arbitrary quantum state is a problem of significant complexity [7, 8]. Thus, witnessing entanglement by using versatile experimentally feasible tools [9–18] is a challenging task. In the case of multipartite entanglement, the challenge enhances significantly and demands greater interest from the scientific community. In this paper, we propose a protocol to detect multipartite entanglement by utilizing the well-known phenomenon of non-Markovianity in open quantum systems [19, 20] and the theory of positive maps. The positive maps that are not completely positive can detect bipartite entanglement quite effectively, Partial Transposition [21] being a well-known example. Unfortunately, this technique cannot be directly extended to the case of multipartite entanglement, where diverse separability structures complicate the detection problem. Although semi-definite programming can be used to construct witnesses to certify genuine multipartite entangle

Abstract

In the left-right symmetric models, a heavy charged gauge boson can decay to a lepton and a right-handed neutrino (RHN). If the neutrino masses are generated through the standard type-I seesaw mechanism, the Yukawa couplings controlling two-body decays of the RHN become very small. As a result, the RHN decays to another lepton and a pair of jets via an off-shell . This is the basis of the Keung-Senjanovi'{c} (KS) process, which was originally proposed as a probe of lepton number violation at the LHC. However, if a different mechanism like the inverse seesaw generates the neutrino masses, a TeV-scale RHN can have large Yukawa couplings and hence, dominantly decay to a lepton and a boson, leading to a kinematically different process from the KS one. We investigate the prospect of this unexplored process as a probe of the inverse seesaw mechanism in the left-right symmetric models at the HL-LHC. Our signal arises from the Drell-Yan production of a and leads to two high- same-flavour-opposite-sign leptons and a boosted -like fatjet in the final state. We find that a sequential with mass up to ~TeV along with a TeV-scale RHN can be discovered at the HL-LHC.

Abstract

Recently leptoquarks (LQs) are receiving a lot of attention in the literature. Since they connect the quark and the lepton sectors of the Standard Model (SM), their phenomenology is interesting in general. However, the recent attention is mainly due to their ability to explain the long-standing anomalies observed in B-meson decays and the muon anomalous magnetic moment measurements (see, e.g., [1–34] for a few recent studies). Generally, the models explaining the anomalies contain LQs that couple with the third-generation quarks and leptons. This gives additional motivation to search for such LQs (commonly known as the third-generation LQs in the literature) at the Large Hadron Collider (LHC). Various strategies have already been applied in the searches for third-generation LQs at the LHC [

Abstract

Search strategies for the third-generation leptoquarks (LQs) are distinct from other LQ searches, especially when they decay to a top quark and a τ lepton. We investigate the cases of all TeV-scale scalar and vector LQs that decay to either a top-tau pair (charge-1/3 and 5/3 LQs) or a top-neutrino pair (charge2/3 LQs). One can then use the boosted top (which can be tagged efficiently using jet-substructure techniques) and high-pT τ leptons to search for these LQs. We consider two search channels with either one or two taus along with at least one hadronically decaying boosted top quark. We estimate the high luminosity LHC (HL-LHC) search prospects of these LQs by considering both symmetric and asymmetric pair and single production processes. Our selection criteria are optimised to retain events from both pair and single production processes. The combined signal has better prospects than the traditional searches. We include new three-body single production processes to enhance the single production contributions to the combined signal. We identify the interference effect that appears in the dominant single production channel of charge-1/3 scalar LQ (S 1/3 ). This interference is constructive if S 1/3 is weak-triplet and destructive, for a singlet one. As a result, their LHC prospects differ appreciably

Abstract

The U1 leptoquark (LQ) is known to be a suitable candidate for explaining the semileptonic B-decay anomalies. We derive precise limits on its parameter space relevant for the anomalies from the current LHC high-pT dilepton data. We consider an exhaustive list of possible B-anomalies-motivated simple scenarios with one or two new couplings that can also be used as templates for obtaining bounds on more complicated scenarios. To obtain precise limits, we systematically consider all possible U1 production processes that can contribute to the dilepton searches including the resonant pair and single productions, nonresonant t-channel U1 exchange, as well as its large interference with the Standard Model background. We demonstrate how the inclusion of generally ignored resonant productions and signal-background interference contributions in the dilepton signal can lead to stringent exclusion limits. We point out new search channels of U1 that can act as unique tests of the flavour-motivated models. The template scenarios can also be used for future U1 searches at the LHC. We compare the LHC limits with other relevant flavor bounds and find that a TeV-scale U1 can accommodate both RD(∗) and RK(∗) anomalies while satisfying all the bounds.

Abstract

Most of the popular explanations of the observed anomalies in the semileptonic B-meson decays involve TeV scale Leptoquarks (LQs). Among the various possible LQ models, two particular LQs—S1(3, 1, 1/3) and U1(3, 1, 2/3) seem to be most promising. Here, we use current LHC data to constrain the S1(3, 1, 1/3) and U1(3, 1, 2/3) parameter spaces relevant for the RD(∗) observables. We recast the latest ATLAS τ τ resonance search data to obtain new exclusion limits. For this purpose, we consider both resonant (pair and single productions) and non-resonant (t-channel LQ exchange) productions of these LQs at the LHC. For the limits, the most dominant contribution comes from the (destructive) interference of the nonresonant production with Standard Model backgrounds. The combined contribution from the pair and inclusive single production processes Mandal et al (JHEP, 07:028, 2015, [1]) is less prominent but non-negligible. The limits we get are independent and competitive to other known bounds. For both the models, we set limits on RD(∗) motivated couplings Mandal et al (Phys Rev D 99(5):055028, 2019, [2]), Bhaskar et al (Phys Rev D 104(3):035016, 2021, [3]).

Abstract

The Standard Model (SM), when extended with a leptoquark (LQ) and right-handed neutrinos, can have interesting new implications for Higgs physics. We show that sterile neutrinos can induce a boost to the down-type quark Yukawa interactions through a diagonal coupling associated with the quarks and a scalar LQ of electromagnetic charge 1/3. The relative change is moderately larger in the case of the first two generations of quarks, as they have vanishingly small Yukawa couplings in the SM. The enhancement in the couplings would also lead to a non-negligible contribution from the quark fusion process to the production of the 125 GeV Higgs scalar in the SM, though the gluon fusion always dominates. However, this may not be true for a general scalar. As an example, we consider a scenario with a SM-gauge-singlet scalar ϕ where an O (1) coupling between ϕ and the LQ is allowed. The ϕ q q Yukawa …

Abstract

Motivated by the RDð
Þ anomalies, we investigate an SO(10) grand unification scenario where a charge −1=3 scalar leptoquark (S1) remains as the only new physics candidate at the TeV scale. This leptoquark along with the Standard Model (SM) Higgs doublet originates from the same ten-dimensional real scalar multiplet in the SO(10) grand unification framework taking its mass close to the electroweak scale. We explicitly show how the gauge coupling unification is achieved with only one intermediate symmetrybreaking scale at which the Pati-Salam gauge group is broken into the SM group. We investigate the phenomenological implications of our scenario and show that an S1 with a specific Yukawa texture can explain the RDð
Þ anomalies. We perform a multiparameter scan considering the relevant flavor constraints on RDð
Þ , FLðD
Þ, PτðD
Þ and Rνν Kð
Þ as well as the constraint coming from the Z → ττ decay and the latest ττ resonance search data at the LHC. Our analysis shows that a single leptoquark solution to the observed RDð
Þ anomalies with S1 is still a viable solution.