In this letter, I propose a strategy to measure vector-boson scattering (VBS) at the LHCb experiment. The typical VBS topology at hadron colliders features two energetic back-to-back jets with large rapidities and two gauge bosons produced centrally. In this article, I show that such a topology can actually be probed by the LHCb detector. In particular, tagging only one of the two jets in combination with two same-sign leptons allows for a measurement with upcoming luminosities. I present an illustrative event selection where cross sections and differential distributions are computed for VBS and its irreducible background.
We study the possibility of observing a light pseudo-scalar $a$ at LHCb. We target the mass region $1 \lesssim m_a \lesssim 60$ GeV and various decay channels, some of which have never been considered before: muon pairs, tau pairs, $D$ meson pairs, and di-photon. We interpret the results in the context of models of 4D Composite Higgs and Partial Compositeness in particular.
LHCb provides unique opportunities to study $W$ and $Z$ boson production at forward rapidities at the LHC. It has recently been suggested that a measurement of the $W$ boson mass by LHCb would complement measurements by ATLAS and CMS. All measurements of the $W$ mass at hadron colliders are subject to PDF uncertainties, but there would be a partial cancellation of the overall PDF uncertainty when the LHCb result is included in an average with measurements by ATLAS and CMS. Here we review measurements of $W$ and $Z$ boson production by LHCb, and report on a new study of the PDF uncertainty on t…
Because of its forward coverage, LHCb can probe the valence quark distributions of protons and nuclei at small and large Bjorken-x with high precision. This proceeding presents new LHCb measurements of Z boson production in association with charm jet in the forward region of proton-proton collisions and Z boson production in proton-lead collisions. Z+charm jet production could be sensitive to a valence-like intrinsic-charm component in the proton wave function. The measurements of Z production in proton-lead collisions provide new constraints on the partonic structure of nucleons inside nuclei…
In this high-$x$ region, both the flavour content and structure of the nucleon parton distribution functions remains relatively poorly known. New LHCb measurements of Z and charm jet associated production could indicate a valence-like intrinsic-charm component in the proton wave function, and measurements of Z production in pPb collisions provide new constraints on the partonic structure of nucleons bound inside nuclei. Here we will discuss these new LHCb measurements and comparisons with state-of-the-art parton distribution function calculations.
A range of flavour physics observables show tensions with their corresponding Standard Model expectations: measurements of leptonic flavour-changing neutral current processes and ratios of semi-leptonic branching fractions involving different generations of leptons show deviations of the order of four standard deviations. If confirmed, either would be an intriguing sign of new physics. In this manuscript, we analyse the current experimental situation of such processes and for the first time estimate the combined impact of the future datasets of the Belle II and LHCb experiments on the present …
Precision electroweak tests are a powerful probe of physics beyond the Standard Model, but the sensitivity is limited by the precision with which the $W$ boson mass ($M_W$) has been measured. The Parton Distribution Function (PDF) uncertainties are a potential limitation for measurements of $M_W$ with LHC data. It has recently been pointed out that, thanks to LHCb's unique forward rapidity acceptance, a new measurement of $M_W$ by LHCb can improve this situation. Here we report on a detailed study on the mechanism driving the PDF uncertainty in the LHCb measurement of $M_W$, and propose an app…
At LHCb, proton parton distribution functions (PDFs) can be studied in a unique phase space complementary to that accessible by ATLAS and CMS, corresponding to low and high values of Bjorken-$x$. The measurements of vector boson production in the forward region, with and without an associated jet, are presented. These measurements can be used to constrain the proton PDFs, and in particular, the production of a $Z$ boson in association with a $c$-jet can be studied to measure the intrinsic charm content of the proton.
This paper reports a study of the experimental signatures of hierarchical sectors beyond the Standard Model characterized by a flavor-violating heavy vector and a set of light pseudo-Goldstone bosons $a_{1,2}$, spanning a large range of lifetimes. The non-minimal scalar spectrum triggers novel $B$ decays into multiple leptons that would have escaped the reach of current searches. Novel displaced vertex analyses at LHCb are therefore discussed to probe the hierarchical new physics, extending the scope of the tracking system of the detector. Additionally, the reach of the proposed CODEX-b experi…
A peak structure of $J/ψ$ pair production around $6.9~{\rm GeV}$ was observed and analyzed by the LHCb collaboration using the Run I and II data of LHC. How to understand this peak arouses enthusiastic discussions among both theorists and experimentalists of high energy physics, because this discovery might hint something new. Overwhelming works on this topic tend to attribute the peak as a four-quark state: tetraquark or molecule. Instead, we suggest that this peak is corresponding to a fundamental Higgs-like boson with mass about $6.9~{\rm GeV}$ which is advocated by a BSM effective theory. …
We study the potential of the LHCb 13 TeV single $W^{\pm}$ and $Z$ boson pseudo-data for constraining the parton distribution functions (PDFs) of the proton. As an example, we demonstrate the sensitivity of the LHCb 13 TeV data, collected with integrated luminosities of 5 fb$^{-1}$ and 300 fb$^{-1}$, to reducing the PDF uncertainty bands of the CT14HERA2 PDFs, using the error PDF updating package {\sc ePump}. The sensitivities of various experimental observables are compared. Generally, sizable reductions in PDF uncertainties can be observed in the 300 fb$^{-1}$ data sample, particularly in th…
Stimulated by the new discovery of $P_{c}(4312)^{+}$ by LHCb Collaboration, we endeavor to perform the study of $P_{c}(4312)^{+}$ as a $Σ_{c}\bar{D}$ state in the framework of QCD sum rules. Taking into account the results from two sum rules, a conservative mass range $4.07\sim4.97~\mbox{GeV}$ is presented for the $Σ_{c}\bar{D}$ hadronic system, which agrees with the experimental data of $P_{c}(4312)^{+}$ and could support its interpretation as a $Σ_{c}\bar{D}$ state.
We propose a novel process where singly charged Higgs bosons are produced in a same-sign pair via vector boson fusion at hadron colliders in two Higgs doublet models. The process directly relates to the global symmetry structure of the Higgs potential. The produced charged Higgs bosons predominantly decay into a tau lepton and the neutrino or into a pair of top and bottom quarks, depending on the type of Yukawa interactions. We evaluate the signal and the background for the both cases at the CERN Large Hadron Collider and future higher-energy hadron colliders. We find that the process can be f…
We present a comprehensive investigation on the possibility of the search for new force mediator $X$ boson in $e^+e^-$ collision and $J/ψ$ decay at the BESIII experiment. The typical interactions of $X$ boson coupling to leptons and quarks are explored. The production and decay properties of this $X$ particle, the product/decay chains $e^+e^-\to Xγ\to e^+e^-γ$ and $J/ψ\to Xγ\toμ^+μ^-γ$, and exclusion limits on the reduced coupling strength parameters as functions of $X$ boson mass are presented. With the data set of tens of fb$^{-1}~e^+e^-$ or $10^{10}~J/ψ$, we find that the exclusion limits o…
Very recent experimental information obtained from the Belle experiment, along with that accumulated by the BABAR and LHCb experiments, has shown the existence of anomalies in the ratios $R(D)$ and $R(D^{*})$ associated with the charged-current transition $b \to c τ\barν_τ$. Although the Belle measurements are in agreement with the standard model (SM) predictions, the new experimental world averages still exhibit a tension. In addition, the $D^\ast$ longitudinal polarization $F_L(D^\ast)$ related with the channel $B \to D^\ast τ\barν_τ$ observed by the Belle Collaboration and the ratio $R(J/ψ)…
We discuss scenarios with wrong-sign (WS) Yukawa couplings for the discovered Higgs boson in the Yukawa-aligned two Higgs doublet model. In the WS scenario, Yukawa couplings for down-type quarks and/or charged leptons have an opposite sign as compared to those of the Higgs boson in the standard model, which can be consistent with current flavour data and the Higgs signal strengths. The phenomenology of additional Higgs bosons in such a scenario can be significantly different from that with right-sign Yukawa couplings, mainly due to a larger Higgs boson mixing to be required in the wrong-sign c…
$Z^0$-boson production at low transverse momentum offers an unique opportunity to explore the non-perturbative Sudakov factor. In this paper, we employ three parameterizations of the non-perturbative Sudakov factor to calculate the $ϕ^*$-distribution and compare our results with the ultra precise experimental data. We extract the free parameters in each parameterization with a $χ^2$ analysis. The parton-momentum-fraction dependence of these free parameters is also studied by comparing the values extracted at different collision energies and different rapidity ranges.
We propose a new search strategy for higgsinos. Assuming associated production of higgsino-like pairs with a $W$ or $Z$ boson, we search in the missing energy plus hadronically-tagged vector boson channel. We place sensitivity limits for (HL-)LHC searches assuming $\mathcal{O}({1\mathrm{-}3.5}~\mathrm{GeV})$ mass differences between the lightest neutral and charged states. We point out that using the $E_T^\mathrm{miss}$ distribution significantly increases the sensitivity of this search. We find the higgsinos up to 110 (210) GeV can be excluded with $139~(300)~\mathrm{fb}^{-1}$ data. The full …
We study the impact of fermionic dark matter (DM) on projected Higgs precision measurements at the Circular Electron Positron Collider (CEPC), including the one-loop effects on the $e^+e^-\to Zh$ cross section and the Higgs boson diphoton decay, as well as the tree-level effects on the Higgs boson invisible decay. As illuminating examples, we discuss two UV-complete DM models, whose dark sector contains electroweak multiplets that interact with the Higgs boson via Yukawa couplings. The CEPC sensitivity to these models and current constraints from DM detection and collider experiments are inves…
We classify shapes of Higgs boson pair invariant mass distributions $m_{hh}$, calculated at NLO with full top quark mass dependence, and visualise how distinct classes of shapes relate to the underlying coupling parameter space. Our study is based on a five-dimensional parameter space relevant for Higgs boson pair production in a non-linear Effective Field Theory framework. We use two approaches: an analysis based on predefined shape types and a classification into shape clusters based on unsupervised learning. We find that our method based on unsupervised learning is able to capture shape fea…
The recent measurements on $R_D$, $R_{D^*}$ and $R_{J/ψ}$ by three pioneering experiments, BaBar, Belle and LHCb, indicate that the notion of lepton flavour universality is violated in the weak charged-current processes, mediated through $b \to c \ell \bar ν_\ell$ transitions. These intriguing results, which delineate a tension with their standard model predictions at the level of $(2-3)σ$ have triggered many new physics propositions in recent times, and are generally attributed to the possible implication of new physics in $ b \to c τ\bar ν$ transition. This, in turn, opens up another avenue,…
In this study, we explore the detectability of heavy Higgs bosons in the $pp \to b\bar{b}H/A \to b\bar{b}t\bar{t}$ channel at a 100 TeV hadron collider within the semi-constrained Next-to-Minimal Supersymmetric Standard Model (NMSSM). We calculate their production cross sections and decay branching ratios, comparing these with simulation results from existing reference. We focus on the heavy, doublet-dominated CP-even Higgs $H$ and CP-odd Higgs $A$, with mass limits set below 10 TeV to ensure detectability. We find that at a collider with 3 ab$^{-1}$ of integrated luminosity, the potential for…
We study an economical model of weakly-interacting massive particle dark matter (DM) which has spin 3/2 and interacts with the 125-GeV Higgs boson via effective scalar and pseudoscalar operators. We apply constraints on the model from the relic density data, LHC measurements of the Higgs boson, and direct and indirect searches for DM, taking into account the effective nature of the DM-Higgs couplings. We show that this DM is currently viable in most of the mass region from about 58 GeV to 2.3 TeV and will be probed more stringently by ongoing and upcoming experiments. Nevertheless, the presenc…
The Standard Model effective field theory (SMEFT) provides a general framework to include the dynamics of the beyond standard model physics residing at a certain higher energy scale $Λ$. We study the top-quark production along with a Higgs boson and a jet (tHq) at the LHC experiment within the framework of the SMEFT. First, identifying the relevant sensitive dimension-6 SMEFT operators, a strategy is developed to constrain the Wilson Coefficients (WC) corresponding to these associated SMEFT operators using the latest LHC measurements, providing a complementary way to the global-fit approach. T…
Exploring the Singlino-dominated Thermal Neutralino Dark Matter in the $Z_3$ invariant NMSSM
SRM University-AP（SRM大学-安得拉邦）；Aix Marseille Univ., Université de Toulon, CNRS, CPT, IPhU（艾克斯-马赛大学、土伦大学、法国国家科学研究中心、理论物理中心、统一粒子物理研究所）；Kavli IPMU (WPI), UTIAS, The University of Tokyo（卡弗里宇宙起源原初物理学国际研究中心（世界顶尖科学家计划）、东京大学航空宇宙工程学研究所）；Centre for High Energy Physics, Indian Institute of Science（印度理工学院高能物理中心）
An important task at future colliders is the measurement of the triple Higgs coupling. Depending on its size relative to the Standard Model (SM) value, certain collider options result in a higher experimental accuracy. Within the framework of Two Higgs Doublet Models (2HDM) type I and II we investigate the allowed ranges for all triple Higgs couplings involving at least one light, SM-like Higgs boson. We take into account theoretical constraints (unitarity, stability), experimental constraints from direct Higgs-boson searches, measurements of the SM-like Higgs-boson properties, flavor observab…
We investigate the possibility of detectable 2-Higgs Doublet Model (2HDM) type-II cross-sections at the High-Luminosity phase of the Large Hadron Collider (HL-LHC) for the production of the Standard Model (SM)-like Higgs boson ($h$) in association with a single top (anti)quark over the parameter space region corresponding to the so-called `wrong-sign solution' of the bottom (anti)quark Yukawa coupling. We isolate the latter by using the toolbox Magellan, which performs Markov Chain Monte Carlo (MCMC) scans in the presence of all current theoretical and experimental constraints, which relevance…
