Combining the $b\to sμ^+μ^-$ anomaly and dark matter observables, we study the capability of LHC to test dark matter, $Z^{\prime}$, and vector-like quark. We focus on a local $U(1)_{L_μ-L_τ}$ model with a vector-like $SU(2)_L$ doublet quark $Q$ and a complex singlet scalar whose lightest component $X_I$ is a candidate of dark matter. After imposing relevant constraints, we find that the $b\to sμ^+μ^-$ anomaly and the relic abundance of dark matter favor $m_{X_I}< 350$ GeV and $m_{Z^{\prime}}< 450$ GeV for $m_Q<$ 2 TeV and $m_{X_R}<$ 2 TeV (the heavy partner of $m_{X_I}$). The current searches for jets and missing transverse momentum at the LHC sizably reduce the mass ranges of the vector-like quark, and $m_Q$ is required to be larger than 1.7 TeV. Finally, we discuss the possibility of probing these new particles at the high luminosity LHC via the QCD process $pp \to D\bar{D}$ or $pp \to U\bar{U}$ followed by the decay $D\to s (b) Z'X_I$ or $U \to u (c) Z' X_I$ and then $Z'\toμ^+μ^-$. Taking a benchmark point of $m_Q$=1.93 TeV, $m_{Z^\prime}=170$ GeV, and $m_{X_I}=$ 145 GeV, we perform a detailed Monte Carlo simulation, and find that such benchmark point can be accessible at the 14 TeV LHC with an integrated luminosity 3000 fb$^{-1}$.
This paper discusses model-agnostic searches for new physics at the Large Hadron Collider (LHC) using anomaly-detection techniques for the identification of event signatures that deviate from the Standard Model (SM). We investigate anomaly detection in the context of machine-learning approaches using autoencoders, and illustrate expected shapes of invariant masses in the outlier region using Monte Carlo simulations. Challenges and conceptual limitations of this approach are discussed.
The ATLAS and CMS collaborations recently reported indication of a Higgs boson around 125 GeV. If we add extra vector-like quarks to the MSSM, such a relatively heavy Higgs can be naturally realized in the GMSB framework, simultaneously explaining the muon g-2 anomaly. I will discuss LHC prospects of this attractive model.
Exchanging a $Z^\prime$ gauge boson is a favored mechanism to solve the muon $(g-2)_μ$ anomaly. Among such models the $Z^\prime$ from $U(1)_{L_μ- L_τ}$ gauge group has been extensively studied. In this model the same interaction addressing $(g-2)_μ$, leads to an enhanced muon neutrino trident (MNT) process $ν_μN \to ν_μμ\bar μN$ constraining the $Z^\prime$ mass to be less than a few hundred MeV. Many other $Z^\prime$ models face the same problem. It has long been realized that the coupling of $Z^\prime$ in the model can admit $(\bar μγ^μτ+ \bar ν_μγ^μL ν_τ)Z^\prime_μ$ interaction which does no…
If SUSY is discovered at the LHC, the task will immediately turn to determining the model of SUSY breaking. Here, we employ a Mixed Modulus-Anomaly Mediated SUSY Breaking (MMAMSB) model with very similar LHC phenomenology to the more conventionally studied Constrained Minimal SUSY Model (CMSSM) and minimal Anomaly Mediated SUSY Breaking (mAMSB) models. We then study whether the models can be distinguished and measured. If we only fit to the various mass edges and mass end-points from cascade decay chains that are normally studied, a unique determination and measurement of the model is problema…
We investigate the rare radiative decays of extra gauge neutral bosons. In particular, we established the theoretical predictions for the production of unparticle in decays of $Z^{\prime}$ - bosons. The implementation of our prediction in the analysis at the LHC experiments should be straightforward and lead to more precise determination or limits of unparticle couplings and/or $Z^{\prime}$ couplings and masses.
We consider the contribution of radially excited 2^3P_{1,2} states to psi^prime production at the Tevatron energy. Production of these states via the conventional gluon fusion mechanism and via gluon and charm quark fragmentation processes is considered. We find that it is possible to account for the data on psi^prime production from the CDF experiment, by taking into account the decays of these 2^3P_{1,2} states into psi^prime.
In the anomaly-mediated supersymmetry breaking model with the assumption of the generic form of Kahler potential, gauginos are the only kinematically accessible superparticles to the LHC. We consider the LHC phenomenology of such a model assuming that the gluino is lighter than 1 TeV. We show that a significant number of charged Winos, which may travel O(10 cm) before the decay, are produced from the gluino production processes. Thus, in this class of model, it will be very important to search for short charged tracks using inner detectors. We also show that, if a large number of the charged W…
We point out that slepton pairs produced via gauge boson fusion in anomaly mediated supersymmetry breaking (AMSB) model have very characteristic and almost clean signal at the Large Hadron Collider. In this article, we discuss how one lepton associated with missing energy and produced in between two high-$p_T$ and high-mass forward jets can explore quite heavy sleptons in this scenario.
Many new physics models predict the existence of TeV-scale charged gauge boson $W^\prime$ together with Higgs boson(s). We study the $W^\prime WH$ interaction and explore the angular distribution of charged lepton to distinguish $W_R^\prime WH$ from $W_L^\prime WH$ in $pp\to HW\to b \bar b l ν$ process at the LHC. It is found that a new type forward-backward asymmetry($A_{FB}$) relating to the angle between the direction of the charged lepton in $W$ rest frame and that of the reconstructed $W^\prime$ in laboratory frame is useful to investigate the properties of $W^\prime W H$ interaction. We …
In this thesis we examine three different models in the MSSM context, all of which have significant supergravity anomaly contributions to their soft masses. These models are the so-called Minimal, Hypercharged, and Gaugino Anomaly Mediated Supersymmetry Breaking models. We explore some of the string theoretical motivations for these models and proceed by understanding how they would appear at the Large Hadron Collider (LHC). Our major results include calculating the LHC reach for each model's parameter space and prescribing a method for distinguishing the models after the collection of 100 fb^…
We compute the decay rates for the exclusive decays $B^{\pm} \to (η^{\prime},η) (K^{\pm}, K^{*\pm})$ and $B^{0}\to (η^{\prime},η) (K^{0}, K^{*0})$ in a QCD-improved factorization framework by including the contribution from the process $b\to sgg \to s (η^{\prime}, η)$ through the QCD anomaly. This method provides an alternative estimate of the contribution $b \to s c\bar{c} \to s(η,η^\prime)$ to these decays as compared to the one using the intrinsic charm content of the $η^{\prime}$ and $η$ mesons determined through the decays $J/ψ\to (η,η^\prime ,η_c) γ$. The resulting branching ratios are c…
Stringent experimental constraints have raised the lower limit on the masses of squarks to TeV levels, while compatibility with the mass of the Higgs boson provides an upper limit. This two-sided bound has lead to the emergence of Mini-Split theories where gauginos are not far removed from the electroweak scale while scalars are somewhat heavier. This small hierarchy modifies the spectrum of standard anomaly and gauge mediation, leading to Mini-Split deflected anomaly and gauge mediation models. In this paper, we study LHC constraints on these models and their prospects at LHC 14 and a 100 TeV…
The experimental hint of large $B\to η^\prime + X_s$ is linked to the $b\to s$ penguins via the gluon anomaly. Using running $α_s$ in the $η^\prime$-$g$-$g$ coupling, the standard $b\to sg^*$ penguin alone seems insufficient, calling for the need of dipole $b\to sg$ at 10% level from new physics, which could also resolve the ${\cal B}_{s.l.}$ and charm counting problems. The intereference of standard and new physics contributions may result in direct CP asymmetries at 10% level, which could be observed soon at B Factories.
The $P_5'$ anomaly uncovered by the LHCb experiment in $B \to K^*μμ$ angular observables has motivated a possible $Z'$ boson that couples to left-handed $b \to s$ transitions, where a model would be gauged $L_μ- L_τ$ symmetry, but direct search for such a $Z'$ is not promising. Less constrained is an analogous $Z'$ coupling to right-handed $t \to c$ transitions. Motivated by this, we study $cg \to tZ'$ associated production at LHC, both for a generic model, and in $L_μ- L_τ$ with a vector-like U quark. We also study $c\bar c \to Z'$ production that exists within the model. Both processes can b…
We analyse the possibilities to detect a new $Z^{\prime}$ boson in di-electron events at Tevatron and LHC in the framework of the 331 model with right-handed neutrinos. Using $p\bar{p}$ collision data collected by the CDF II detector at Fermilab Tevatron, we find that the 331 $Z^{\prime}$ boson is excluded with masses below 920 GeV. For an integrated luminosity of $100 fb^{-1}$ at LHC, and considering a central value $M_{Z^{\prime}}=1500$ GeV, we obtain the invariant mass distribution in the process $pp\to Z^{\prime}\to e^{+}e^{-}$, where a huge peak, corresponding to 800 signal events, is fou…
Motivated by the $R_K$ and $R_{K^*}$ anomalies from B decays, we extend the minimal supersymmetric model with a non-universal anomaly-free $U(1)^\prime$ gauge symmetry, coupling non-universally to the lepton sector as well as the quark sector. In particular, only the third generation quarks are charged under this $U(1)^\prime$, which can easily evade the dilepton bound from the LHC searches. An extra singlet is introduced to break this $U(1)^\prime$ symmetry allowing for the $μ$-term to be generated dynamically. The relevant constraints of $B_s-\bar{B}_s$ mixing, $D^0-\bar{D}^0$ mixing and the…
Sneutrino-antisneutrino oscillation can be observed at the LHC by studying a charge asymmetry of the leptons in the final states. We demonstrate this in the context of an anomaly-mediated supersymmetry breaking model which can give rise to a large oscillation probability. The preferred region of the parameter space is characterized by the presence of a sneutrino next-to-lightest supersymmetric particle and a stau lightest supersymmetric particle. We show that the signals studied here have certain correlations with the pattern of the sneutrino oscillation.
The Forward-Backward Asymmetry (AFB) in $Z^\prime$ physics is commonly only perceived as the observable which possibly allows one to interpret a $Z^\prime$ signal by distinguishing different models of such (heavy) spin-1 bosons. In this article, we examine the potential of AFB in setting bounds on or even discovering a $Z^\prime$ at the Large Hadron Collider (LHC) and show that it might be a powerful tool for this purpose. We analyze two different scenarios: $Z^\prime$s with a narrow and wide width, respectively. We find that in both cases AFB can complement the cross section in accessing $Z^\…
The singlet pseudoscalar sector of light mesons is investigated in the soft-wall model, a bottom-up approach to the AdS/QCD correspondence. The $η^\prime$ mass results from the mixing among the fields dual to the axial current, pseudoscalar current and the $G\tilde G$ operator. The topological susceptibility is computed for any quark mass, and the Witten-Veneziano relation is obtained in the large $N_c$ limit.
Non-universal gaugino mass models can naturally account for the dark matter relic density via the bulk annihilation process with relatively light bino LSP and right sleptons in the mass range of ~ 100 GeV, while accommodating the observed Higgs boson mass of ~ 125 GeV with TeV scale squark/gluino masses. A class of these models can also account for the observed muon g-2 anomaly via SUSY loops with wino and left sleptons in the mass range of 400 -- 700 GeV. These models can be tested at LHC via electroweak production of charged and neutral wino pair, leading to robust trilepton and same sign di…
Sneutrino-antisneutrino oscillation can be observed at the LHC by studying a charge asymmetry of the leptons in the final states. In this talk, we demonstrate this in the context of an anomaly-mediated supersymmetry breaking model which can give rise to a large oscillation probability. The preferred region of the parameter space is characterized by the presence of a sneutrino next-to-lightest supersymmetric particle and a stau lightest supersymmetric particle. We show that the signals studied here have certain correlations with the pattern of the sneutrino oscillation.
We enumerate various effective couplings that contribute to the mixings between an exotic vector boson $Z^{\prime}$ and the neutral electroweak vector bosons. The miscellaneous mixing patterns can be evaluated perturbatively. The effective oblique parameters $S^{\prime}$, $T^{\prime}$, and $U^{\prime}$ are calculated to compare with the electroweak precision test results. With the contributions to the non-negligible $U^{\prime}$ parameter from the $ε_{B,W}$ parameters and the aid of some other parameters to cancel the negative $T^{\prime}$, the recent CDF $W$-mass anomaly can therefore be expl…
A variety of new physics models predict the existence of extra charged gauge bosons ($W^\prime$). It is verified that $W^\prime$ and top quark associated production is a promising process to search for $W^\prime$ signal at the LHC. We study the collider signatures of multi-jets$+$lepton$+\met$ by reconstructing the $tW'$ intermediate state through the decay modes of $W^\prime \to tb$, $W^\prime \to q \bar q'$ and $W^\prime \to l ν$ respectively. An angular distribution related to charged lepton and top quark moving direction is provided to distinguish alternative left-handed or right-handed ch…
The ground-state (lightest) hybrid nonet with exotic quantum numbers $J^{PC}=1^{-+}$ and the nonet of their chiral partners with $J^{PC}=1^{+-}$ build a homochiral multiplet involving left- and right-handed currents, which under chiral transformation change just as (axial-)vector mesons. Masses and interactions of hybrids can be obtained in the context of the extended Linear Sigma Model. Here, we concentrate on the decays oh hybrids into two pseudoscalar mesons, such as $ηπ$ and $η^{\prime}π$ modes. Indeed, $π_{1}(1400)\rightarrowπη$ and $π_{1}(1600)\rightarrowπη^{\prime}$ have been seen in ex…
Combining anomaly with $Z^\prime$ mediation allows us to solve the tachyonic problem of the former and avoid fine tuning in the latter. This model includes an extra $U(1)^\prime$ gauge symmetry and extra singlet scalar $S$ which provides a solution to the `$μ$ problem' of the Minimal Supersymmetric Standard Model (MSSM). The low-energy particle spectrum is calculated from the UV inputs using the Renormalization Group Equations. The benchmark points considered in the original model, suggested before the Higgs discovery, predicted a Higgs mass heavier than the generic MSSM value. In 2012, the Hi…
We study the sensitivity of a down type quark $b^{\prime}$ via process $pp\rightarrow b^{\prime}\bar{b^{\prime}} \rightarrow tW^-\bar{t}W^+$ using jet substructure methods at the LHC with the collision energy $\sqrt{s}=14$ TeV. We consider the case that the $b^\prime$ is heavy (say from 800 GeV to 1500 GeV) and concentrate on the feasibility of the full hadronic mode. Both top tagger (the HEP top tagger) and W tagger (the CMS W-tagging) are used to reconstruct all objects in the final states. In order to suppress huge SM background events and take into account various cases with different numb…
Motivated by an anomaly observed in the decay of an excited state of Beryllium by the Atomki collaboration, we study an extension of the Standard Model with a gauged $U(1)'$ symmetry in presence of a 2-Higgs Doublet Model structure of the Higgs sector. We show that this scenario complies with a variety of experimental results and is able to explain the potential presence of a resonant spin-1 gauge boson, $Z'$, with a mass of 17 MeV in the Atomki experimental data, for appropriate choices of $U(1)'$ charges and Yukawa interactions.
The current discrepancy in $R_{D^{(*)}}=BR(\bar{B} \to D^{(*)}τ\barν)/BR(\bar{B}\to D^{(*)} \ell \barν)$ where $\ell=e,\,μ$ may imply a know particle with the mass around the order of TeV. Therefore it is well motivated to test those scenarios at the large hadron collider. Thanks to the size of the discrepancy and the analysis based on the effective field theory, the variety of the possible new physics candidates is limited. We focus on the charged Higgs and leptoquark possibility and discuss the collider physics.
An anomaly-free $U(1)'$ effective Lagrangian as the most common new physics beyond the standard model is proposed to survey the maximal parameter space constrained by electroweak precise measurements at the LEP and direct detection in dilepton decay channel at the LHC at $\sqrt{s}=7$ TeV. By the global fit of effective couplings of $Z$ boson to the SM fermions, $Δ_{11},Δ_{21},g_2Δ_{31}$ related to mixings and $r$ related to $U(1)'$ charge assignment are bounded. The allowed areas are plotted in the not only $r$-$g_2$ but also $m_{Z'}$-$g_2$ planes, which show that a sub-TeV $Z'$ is still permi…
The discovery potential of the LHC is investigated for the minimal anomaly-mediated supersymmetry breaking (mAMSB) scenario, using the ATLAS fast detector simulator, including track reconstruction and particle identification. Generic supersymmetry search cuts are used to map the 5-sigma (and >=10 event) discovery contours in the m_0 - m_3/2 plane. With 100 inverse fb of integrated luminosity the search will reach up to 2.8 TeV in the squark mass and 2.1 TeV in the gluino mass. We generalise a kinematical variable and demonstrate that it is sensitive to the small chargino-LSP mass splitting cha…
We investigate the potential of the Large Hadron Collider (LHC) to probe one of the most compelling Beyond the Standard Model (BSM) frameworks --- Walking Technicolor (WTC), involving strong dynamics and having a slowly running (walking) new strong coupling. For this purpose we use recent LHC Run2 data to explore the full parameter space of the minimal WTC model using dilepton signatures from heavy neutral $Z^{\prime}$ and $Z^{\prime\prime}$ resonances predicted by the model. This signature is the most promising one for discovery of WTC at the LHC for the low-intermediate values of the $\tilde…
Searching for heavy vector bosons $Z^\prime$, predicted in models inspired by Grand Unification Theories, is among the challenging objectives of the LHC. The ATLAS and CMS collaborations have looked for $Z^\prime$ bosons assuming that they can decay only into Standard Model channels, and have set exclusion limits by investigating dilepton, dijet and to a smaller extent top-antitop final states. In this work we explore possible loopholes in these $Z^\prime$ searches by studying supersymmetric as well as leptophobic scenarios. We demonstrate the existence of realizations in which the $Z^\prime$ …
We discuss a test of the CDF dijet anomaly at the LHC. The recent observed dijet mass peak at the CDF is well fitted by a new particle with a mass of around 150 GeV, which decays into two jets. In this paper, we focus on only $Wjj$ signal to avoid model dependence, and comprehensively study the LHC discovery/exclusion reach. We found almost all the models are inconsistent with the result of the LHC, unless only valence quarks contribute the new process. We also discuss further prospects of the LHC search for this anomaly.
We examine the reach of the CERN LHC pp collider for supersymmetric models where the dominant contribution to soft SUSY breaking parameters arises from the superconformal anomaly. In the simplest viable anomaly mediated SUSY breaking (AMSB) model, tachyonic slepton squared masses are made positive by adding a universal contribution m_0^2 to all scalars. We use the event generator ISAJET to generate AMSB signal events as a function of model parameter space. Assuming an integrated luminosity of 10 fb-1, the LHC can reach to values of $m_{\tg}\sim 2.3$ TeV for low values of $m_0$, where the dilep…
A class of extra dimensional models with a warped metric predict tunneling of a massive particle localized on our brane and escaping into additional dimensions. The experimental signature of this effect is the disappearance of the particle from our world, i.e. the particle $\to invisible$ decay. We point out that measurements of $Z\prime \to invisible$ decay width of a new heavy gauge boson $Z\prime$ at the CERN LHC can be effectively used to probe the existence of large extra dimensions. This result enhances motivations for a more sensitive search and study for this decay mode and suggests ad…
We apply Bogoliubov compensation principle to the gauge electro-weak interaction to demonstrate a spontaneous generation of anomalous three-boson gauge invariant effective interaction. The non-trivial solution of compensation equations uniquely defines values of parameters of the theory and the form-factor of the anomalous interaction. The contribution of this interaction to running EW coupling $α_{ew}(p^2)$ gives its observable value $α_{ew}(M_W^2)=0.0374$ in satisfactory agreement to the experiment. The anomalous three-boson interaction gives natural explanation of the well-known discrepancy…
We recognise the appearance of a Focus Point (FP) in the transverse momentum distribution of either leptons originating from a BSM $Z^\prime$-boson decay, after a simple normalisation procedure. Exploring the properties of the FP we will be able to define in a general way a new observable, the Focus Point Asymmetry ($A_{\rm FP}$), which can be used to set constrains on the $Z^\prime$ width. We discuss the potential and the sensitivity of the $A_{\rm FP}$ in as diagnostic tool for $Z^\prime$ physics, considering various $Z^\prime$ phenomenological realisations.
We study the $Z^\prime$ phenomenology for two extensions of the Electroweak Standard Model (SM) which have an extra $U(1)_{B-L}$ gauge factor. We show the capabilities of the LHC in distinguishing the signals coming from these two extensions and both of them from the Standard Model background. In order to compare the behavior of these $B-L$ models we consider the reaction $p + p\longrightarrow μ^+ + μ^- + X$ and compute some observables as the total cross sections, number of events, forward-backward asymmetry, final particle distributions like rapidity, transverse momentum, and dimuon invarian…
$\cal T$-parity in the Little Higgs model could be violated by anomalies that allow the lightest $\cal T$-odd $A_H$ to decay into $ZZ$ and $W^+W^-$. We analyze these anomaly induced decays and the two-particle and the three-particle decay modes of other heavy quarks and bosons in this model which yield unique Large Hadron Collider (LHC) signals with fully reconstructable events. $\cal T$-odd quarks in the Little Higgs model are nearly degenerate in mass and they decay by almost identical processes; however, members of the heavy Higgs triplet follow distinct decay modes. The branching fractions…
We consider a supersymmetric model in which gaugino masses are generated by the anomaly-mediation mechanism while scalar masses are from tree-level supergravity interaction. In such a model, scalar fermions as well as Higgsinos become as heavy as O(10-100TeV) and hence only the gauginos are superparticles kinematically accessible to the LHC. We study how and how well the properties of gauginos can be studied. We also discuss the strategy to test the anomaly-mediation model at the LHC.
Recently, deviations in flavor observables of B -> D(*) tau nu have been shown between the predictions in the Standard Model and the experimental results reported by BaBar, Belle, and LHCb collaborations. One of the solutions to this anomaly is obtained in a class of leptoquark model with a scalar leptoquark boson S_1, which is a SU(3)_c triplet and SU(2)_L singlet particle with -1/3 hypercharge interacting with a quark-lepton pair. With well-adjusted couplings, this model can explain the anomaly and be compatible with all flavor constraints. In such a case, the S_1 boson can be pair-produced …
We use the results of CMS and ATLAS searches for resonances that decay to $τν$ or $tb$ and $τ^+τ^-$ or $t\bar t$ final states to constrain the parameters of non-universal $W^\prime$ and $Z^\prime$ gauge bosons that couple preferentially to the third generation. For the former we consider production from $c\bar{b}$ annihilation and find very weak constraints on the strength of the interaction and only for the mass range between 800 and 1100 GeV from the $pp \to τ_h p_T^{\rm miss}$ channel. The constraints on the latter are much stronger and arise from both $t\bar t$ and $τ^+τ^-$ production. Tre…
The Large Hadron Collider will restart with higher energy and luminosity in 2015. This achievement opens the possibility of discovering new phenomena hardly described by the Standard Model, that is based on two neutral gauge bosons: the photon and the $Z$. This perspective imposes a deep and systematic study of models that predicts the existence of new neutral gauge bosons. One of such models is based on the gauge group $SU(3)_C \times SU(3)_L \times U(1)_N$ called 3-3-1 model for short. In this paper we perform a study with $Z^\prime$ predicted in two versions of the 3-3-1 model and compare t…
In light of the recent 750 GeV diphoton anomaly observed at the LHC, we study the possibility of accommodating the deviation from the standard model prediction based on the recently proposed Gauged Two Higgs Doublet Model. The model embeds two Higgs doublets into a doublet of a non-abelian gauge group $SU(2)_H$, while the standard model $SU(2)_L$ right-handed fermion singlets are paired up with new heavy fermions to form $SU(2)_H$ doublets, and $SU(2)_L$ left-handed fermion doublets are singlets under $SU(2)_H$. An $SU(2)_H$ scalar doublet, which provides masses to the new heavy fermions as we…
Excited beryllium has been observed to decay into electron-positron pairs with a $6.8~σ$ anomaly. The process is properly explained by a 17 MeV proto-phobic vector boson. In present work, we consider a family-nonuniversal $U(1)^{\prime}$ that is populated by a $U(1)^{\prime}$ gauge boson $Z^\prime$ and a scalar field $S$, charged under $U(1)^{\prime}$ and singlet under the Standard Model (SM) gauge symmetry. The SM chiral fermion and scalar fields are charged under $U(1)^{\prime}$ and we provide them to satisfy the anomaly-free conditions. The Cabibbo-Kobayashi-Maskawa (CKM) matrix is reproduc…
We propose a new method to define anomaly scores and apply this to particle physics collider events. Anomalies can be either rare, meaning that these events are a minority in the normal dataset, or different, meaning they have values that are not inside the dataset. We quantify these two properties using an ensemble of One-Class Deep Support Vector Data Description models, which quantifies differentness, and an autoregressive flow model, which quantifies rareness. These two parameters are then combined into a single anomaly score using different combination algorithms. We train the models usin…
The cross section for production at the 7 TeV LHC has been measured. For the first time it therefore becomes possible to measure Z couplings to top quarks. Interpreting the notorious LEP1 anomaly on Z couplings to b quarks in terms of an extra-dimension model, one expects an excess, as large as a factor 2, on the rate which may already become significant with the LHC at 8 TeV data. Other schemes are reviewed which also predict deviations of couplings. The size of the effect and a dramatic increase of the top quarks with the right chirality should confirm our interpretation of the underlying me…
The heavy charged gauge bosons were proposed in the theories beyond standard model. We explore the discovery potential for $W'\to t\bar{b}$ with top quark semi-leptonic decay at the LHC. We concentrate on the new physics signal search with the deviation from the standard model prediction if the resonance peak of $W'$ can not be observed directly. The events of signal with two jets plus one charged lepton and missing energy are simulated together with the dominant standard model backgrounds. In this paper, it is found that suitable cuts on the kinematic observables can effectively suppress the …
We investigate the possibility to detect the scalar Higgs boson decay $H\to b\bar b$ in the associated $Z$ and $b\bar b$ production at the LHC using the $k_T$-factorization QCD approach. Our consideration is based on the off-shell (i.e. depending on the transverse momenta of initial quarks and gluons) production amplitudes of $q^* \bar q^* \to Z H \to Z q^\prime \bar q^\prime$, $q^* \bar q^* \to Z q^\prime \bar q^\prime$ and $g^* g^* \to Z q^\prime \bar q^\prime$ partonic subprocesses supplemented with the Catani-Ciafoloni-Fiorani-Marchesini (CCFM) dynamics of parton densities in a proton. We …
Axial-anomaly effects and chiral phase structure in holographic QCD
Hangzhou Institute for Advanced Study, UCAS（杭州高等研究院，中国科学技术大学）；Institute of Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）；University of Chinese Academy of Sciences (UCAS)（中国科学院大学）；International Center for Theoretical Physics Asia-Pacific (ICTP-AP), UCAS（亚太理论物理中心，中国科学技术大学）；Hunan University（湖南大学）
The lack of evidence for new physics at the Large Hadron Collider so far has prompted the development of model-independent search techniques. In this study, we compare the anomaly scores of a variety of anomaly detection techniques: an isolation forest, a Gaussian mixture model, a static autoencoder, and a $β$-variational autoencoder (VAE), where we define the reconstruction loss of the latter as a weighted combination of regression and classification terms. We apply these algorithms to the 4-vectors of simulated LHC data, but also investigate the performance when the non-VAE algorithms are ap…
We study the direct-detection rate for axial-vectorial dark matter scattering off nuclei in an $\mathrm{SU}(2)\times \mathrm{U}(1)$ invariant effective theory and compare it against the LHC reach. Current constraints from direct detection experiments are already bounding the mediator mass to be well into the TeV range for WIMP-like scenarios. This motivates a consistent and systematic exploration of the parameter space to map out possible regions where the rates could be suppressed. We do indeed find such regions and proceed to construct consistent UV models that generate the relevant effectiv…
