Abstract

Vector leptoquarks (vLQs) are popular candidates for searching for physics beyond the Standard Model (SM). In this paper, we present updated exclusion limits on various vLQ species, accounting for all the relevant production mechanisms at the LHC. In particular, we highlight the critical role of indirect production and its interference with the SM Drell-Yan process. This interference can be constructive or destructive, depending on the specific quantum numbers of the vLQ, and significantly impacts the sensitivity of current searches. Furthermore, we demonstrate that including QCD+⁢QED mixed pair production channels leads to a noticeable shift in model-independent mass limits. Additionally, we examine the validity of the full theory with vLQs and corresponding effective operators in the high mass regime. Overall, our analysis yields a substantial improvement in the exclusion limits on vLQs compared to the existing results in the literature.

Abstract

Leptoquarks (LQs) offer a promising framework for exploring physics beyond the Standard Model (BSM). These particles are currently probed at the LHC, primarily through pair production (PP). Our study improves the LHC exclusion limits by including additional production modes like single productions, t-channel LQ exchange, and its interference with the Standard Model background, sometimes providing more substantial constraints than PP alone. We also account for model-independent production through mixed QCD-QED processes, which can significantly shift the exclusion limits based on the electric charge of the LQs. Furthermore, since LQs often arise alongside other BSM particles, such as vector-like fermions and right-handed neutrinos, we investigate the potential for strong production of these particles along with LQs at the High-Luminosity LHC (HL-LHC), offering new perspectives on collider search strategies.

Abstract

In this study, we propose an interesting production mechanism for Vector-Like Leptons (VLLs) through Leptoquarks (LQs). We explore the prospect of producing them at the High-Luminosity LHC around 3000 fb^-1 through various channels involving both scalar and vector LQs. Here, we have performed an analysis of third-generation VLL. Further, we combine various production channels to enhance the detection sensitivity in SM-heavy backgrounds.

Abstract

This study investigates TeV-scale vector leptoquarks (vLQs) and their contributions to the magnetic dipole moments of charged leptons. Significant parameter space for these LQs is excluded using current LHC data. Among vLQs only U1 and V2 can account for the observed positive shift in (a^mu_exp-a^mu_SM) through a lepton chirality-flipping contribution with
LQ-quark-lepton coupling. These LQs can also fits for the electron dipole moment and atomic-parity violation measurements.

Abstract

The Standard Model (SM) successfully describes particle physics phenomena but leaves several open questions, motivating extensions with new gauge interactions. One such extension is the anomaly-free Leptophobic U(1) model, which introduces a new Z' boson and right-handed neutrinos (RHNs) while avoiding stringent collider constraints. These RHNs, with GeV-scale masses and small mixing with SM neutrinos, can behave as long-lived particles (LLPs), leading to displaced vertex (DV) signatures at colliders. In this work, we analyze DV signatures arising from RHN decays and evaluate the sensitivity of various current and proposed LLP detectors, including CMS, LHCb, MATHUSLA, CODEXb, FACET, FASER, and MAPP. Our results highlight the complementary reach of these experiments, demonstrating their potential to probe new physics beyond the SM.

Abstract

We demonstrate how LHC results can be reinterpreted to establish exclusion limits on leptoquark models by incorporating multiple production mechanisms. We highlight several unexplored leptoquark signatures predicted by well-motivated models that have yet to be investigated by experimentalists.

Abstract

We use a hybrid deep neural network (HDNN) to identify a boosted dark photon jet as a signature of a heavy vectorlike fermionic portal matter (PM) connecting the visible and the dark sectors. In this work, the fermionic PM, which mixes only with the Standard Model (SM) third-generation up-type quark, predominantly decays into a top quark and a dark photon pair. The dark photon then promptly decays to a pair of standard model fermions via the gauge kinetic mixing. We have analyzed two different final states, namely, (i) exactly one tagged dark photon and exactly one tagged top quark jet, and (ii) at least two tagged dark photons and at least one tagged top quark jet at the 13 and 14 TeV LHC center of mass energies. Both these final states receive significant contributions from the pair and single production processes of the top partner. The rich event topology of the signal processes, i.e., the presence of a boosted dark photon and top quark jet pair, along with the fact that the invariant mass of the system corresponds to the mass of the top partner, help us to significantly suppress potential SM backgrounds. We have shown that one can set a 2⁢𝜎 exclusion limit of ∼2.3  TeV on the top partner mass with sin⁡𝜃𝐿 =0.1 and assuming 100% branching ratio of the top partner in the final state with exactly one tagged dark photon and exactly one tagged top quark jet at the 14 TeV LHC center of mass energy assuming 300  fb−1 of integrated luminosity.

Abstract

We investigate the dynamical aspects of the quantum switch and find a particular form of quantum memory emerging out of the switch action. We first analyze the loss of information in a general quantum evolution subjected to a quantum switch and propose a measure to quantify the switch-induced memory. We then derive an uncertainty relation between information loss and switch-induced memory. We explicitly consider the example of depolarizing dynamics and show how it is affected by the action of a quantum switch. For a more detailed analysis, we consider both the control qubit and the final measurement on the control qubit as noisy and investigate the said uncertainty relation. Further, while deriving the Lindblad-type dynamics for the reduced operation of the switch action, we identify that the switch-induced memory actually leads to the emergence of non-Markovianity. Interestingly, we demonstrate that the emergent non-Markovianity can be explicitly attributed to the switch operation by comparing it with other standard measures of non-Markovianity. Our investigation thus paves the way forward to understanding the quantum switch as an emerging non-Markovian quantum memory.

Abstract

We use the spin-boson model to describe the dynamics of a two-level atom interacting with Fabry-Pérot cavity modes. We solve the Schrödinger equation for the system-bath model without the Born-Markov approximation to derive the non-Markovian reduced dynamics of the qubit. We further construct an exact Lindblad-type master equation for it. Similar to the quantum Otto cycle, we construct a non-Markovian quasicyclic process based on the atom-cavity interactions, which we call the quasi-Otto cycle. For judicious choices of input state and parameters, the quasicycle can be more efficient as a quantum engine than the Otto cycle. We also show that if the quasicycle is repeated multiple times, the efficiency of the quasi-Otto engine asymptotically approaches that of the Otto engine.

Abstract

We show that the average of the maximum teleportation fidelities between all pairs of nodes in a large quantum
repeater network is a measure of the resourcefulness of the network as a whole. It can be used to rank networks
of arbitrary topologies, with and without loops. For demonstration purposes, we use simple Werner state-based
models to characterize some fundamental topologies (the star, the chain, some trees, and also the ring and the
complete graph) with this measure in three (semi)realistic scenarios. Most of our results are analytic and apply to
arbitrary network sizes. We identify the parameter ranges where these networks can achieve quantum advantages
and show the large-N behaviors.