Leptoquarks with mass in the region of $550-650$ GeV are a possible candidate for the recent excess seen by CMS in the $eejj$ and $e νjj$ channels. We discuss models where leptoquarks decay primarily to dark matter and jets, thereby giving a branching to charged lepton and jet final states that can match data. The confluence of proton decay constraints, dark matter indirect and direct detection data, and Higgs invisible decay bounds results in a handful of predictive models that will be conclusively verified or excluded in upcoming direct detection experiments. Along the way, we present robust limits on such leptoquark models stemming from the muon magnetic moment using current and projected experiment sensitivities, as well as from $K$ and $B$ meson mixing, and leptonic and semi-leptonic meson decays.
Study of leptoquark pair production at the LHC with the CMS detector
我们研究了CMS探测器在大型强子对撞机标量轻夸克对产生中的发现潜力。目前和未来的排除限制。当Br（LQ_1-> l q）= 100%时，最大轻夸克质量可达1.47 TeV，而当Br（LQ_1-> l q）= 50%时，积分亮度为100 fb-1时，最大轻夸克质量可达1.2 TeV.我们得到了电子和μ子型的leptoquark可比的结果。讨论了高光度下的堆积效应。
We present precision predictions for scalar leptoquark pair production at the LHC. Apart from QCD contributions, included are the lepton $t$-channel exchange diagrams relevant in the light of the recent $B$-flavour anomalies. All contributions are evaluated at next-to-leading order in QCD and improved by resummation, in the threshold regime, of the corrections from soft-gluon radiation at the next-to-next-to-leading-logarithmic accuracy. All corrections are found equally relevant. Furthermore, the impact of different sets of parton distribution functions is discussed. These predictions constit…
In this article, we deal with how to distinguish the signatures of different \LQs at the LHC/FCC if all of them lie within similar mass and coupling range and can be produced at present and future colliders. It has been found that hard scattering cross-sections and angular distributions can be used to differentiate scalar and vector Leptoquarks. On the other hand, final state topology and determination of jet charge can separate \LQs with same spin even from same $SU(2)_L$ multiplet. We performed a PYTHIA8 based analysis considering all the dominant Standard Model (SM) backgrounds at the LHC/F…
We study the phenomenology of a particular leptoquark extension of the Standard Model (SM), namely the doublet-singlet scalar leptoquark extension of the SM (DSL-SM). Besides generating Majorana mass for neutrinos, these leptoquarks contribute to muon and electron $(g-2)$ and various lepton flavour violating processes. Collider signatures of the benchmark points (BPs), consistent with the neutrino oscillation data, anomalous muon/electron magnetic moments, experimental bounds on the charged lepton flavour violation observables, etc., are studied at the LHC/FCC with centre-of-mass energies of 1…
We propose a leptoquark model simultaneously to explain anomalies of muon anomalous magnetic dipole moment and $b\to s μ\barμ$ in light of experimental reports very recently. Here, we satisfy several stringent constraints such as $μ\to eγ$ and meson mixings. In addition, we find these leptoquarks also play an role in generating tiny neutrino masses at one-loop level without introducing any additional symmetries. We have numerical analysis and show how degrees our parameter space is restricted.
We study limits from dilepton searches on leptoquark completions to the Standard Model in the parameter space motivated by anomalies in the $b \rightarrow s$ sector. After a full Run-2 analysis by LHCb, the disparity in lepton flavour violation has disappeared. However, the mismatch in angular distributions as well as in $B_s \rightarrow μ^+ μ^-$ partial width is still unresolved and still implies a possible new physics contribution. We probe three models of leptoquarks -- scalar models $S_3$ and $R_2$ as well as vector leptoquark model $U_1$ using non-resonant dilepton searches to place limit…
At the LHC, the gluon-initiated processes are considered to be the primary source of di-Higgs production. However, in the presence of a new resonance, the light-quark initiated processes can also contribute significantly. In this paper, we look at the di-Higgs production mediated by a new singlet scalar. The singlet is produced in both quark-antiquark and gluon fusion processes through loops involving a scalar leptoquark and right-handed neutrinos. With benchmark parameters inspired from the recent resonant di-Higgs searches by the ATLAS collaboration, we examine the prospects of such a resona…
While the hunt for new states beyond the standard model (SM) goes on for various well motivated theories, the leptoquarks are among the most appealing scenarios at recent times due to a series of tensions observed in $B$-meson decays. We consider $SU(2)$ singlet and triplet scalar leptoquarks separately, which contribute to charged and neutral current $B$-meson decays. Focusing on the single production of these two scalar leptoquarks, we perform a PYTHIA-based simulation considering all the dominant SM backgrounds at the current and future setups of the Large Hadron Collider (LHC). The mono-$b…
A TeV scale leptoquark (LQ) is one of the promising explanations of the recent anomalies in the semileptonic decays of $B$ mesons. Among the various LQs, the vector $\rm{U}_1$ is capable of explaining the anomalies in both $R_{D^{(*)}}$ and $R_{K^{(*)}}$ observables. We use the current LHC data to put bounds on the parameter space of $\rm{U}_1$ relevant for the anomalies. Precise bounds are drawn by recasting the latest $ττ$ and $μμ$ 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.…
We analyse scalar leptoquark pair production at the LHC with predictions including $t$-channel lepton exchange contributions up to next-to-leading order (NLO) in QCD. In particular, we calculate NLO-QCD predictions for off-diagonal production channels, {\it i.e.}\ channels that involve two different leptoquark eigenstates and are driven solely by diagrams involving Standard Model leptons in the $t$-channel at leading order, as opposed to diagonal channels where a pair of the same leptoquark eigenstate is produced. We find that reliable theoretical predictions for both channels require NLO accu…
We introduce a novel mechanism for the leptoquark pair production at LHC that is of a $t$-channel topology and is quark-quark initiated. This mechanism operates under fairly general conditions. One of them is that the two leptoquarks in question couple to the same lepton and the other one is that the fermion numbers of these two leptoquarks differ by two. The strength of the proposed mechanism provides an alternative way to the conventional processes to efficiently constrain the parameter space of the two leptoquark scenarios at LHC whenever the aforementioned conditions are met. We accordingl…
We consider the phenomenological signatures of Simplified Models of Flavourful Leptoquarks, whose Beyond-the-Standard Model (SM) couplings to fermion generations occur via textures that are well motivated from a broad class of ultraviolet flavour models (which we briefly review). We place particular emphasis on the study of the vector leptoquark $Δ_μ$ with assignments $\left({\bf{3}}, {\bf{1}}, 2/3 \right)$ under the SM's gauge symmetry, $SU(3)_C \times SU(2)_L \times U(1)_Y$, which has the tantalising possibility of explaining both $\mathcal{R}_{K^{(\star)}}$ and $\mathcal{R}_{D^{(\star)}}$ a…
Recent progress in calculating lepton density functions inside the proton and simulating lepton showers laid the foundations for precision studies of resonant leptoquark production at hadron colliders. Direct quark-lepton fusion into a leptoquark is a novel production channel at the LHC that has the potential to probe a unique parameter space for large masses and couplings. In this work, we build the first Monte Carlo event generator for a full-fledged simulation of this process at NLO for production, followed by a subsequent decay using the POWHEG method and matching to the parton showers uti…
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 -- $S_{1}(3, 1, 1/3)$ and $U_{1}(3, 1, 2/3)$ seem to be most promising. Here, we use current LHC data to constrain the $S_{1}(3, 1, 1/3)$ and $U_{1}(3, 1, 2/3)$ parameter spaces relevant for the $R_{D^{(*)}}$ observables. We recast the latest ATLAS $ττ$ resonance search data to obtain new exclusion limits. For this purpose, we consider both resonant (pair and single productions) and non-resonant ($t$-channe…
We derive constraints from flavor and LHC searches on charmphilic contributions to the muon anomalous magnetic moment with a single leptoquark. Only the scalar leptoquarks $S_1$ and $R_2$ are relevant for the present analysis. We find that for $S_1$ some parameter space remains consistent at $2σ$ with the Brookhaven National Laboratory measurement of the muon $g-2$, under the assumption that the left-type coupling between the muon and the charm quark is a free parameter. The surviving parameter space is, on the other hand, going to be probed in its entirety at the LHC with 300/fb of luminosity…
We investigate asymmetric leptoquark pair production mechanism at the Large Hadron Collider to advocate its potential relevance to establish reliable constraints on the leptoquark parameter space and its ability to aid in correct identification of these attractive sources of new physics. The main feature of asymmetric pair production that genuinely distinguishes it from the usual leptoquark pair production is given by the fact that the two leptoquarks that are produced in proton-proton collisions through a $t$-channel lepton exchange are not charge conjugates of each other. Hence the proposed …
