M. Guchait

The Supersymmetry Les Houches Accord (SLHA) provides a universal set of conventions for conveying spectral and decay information for supersymmetry analysis problems in high energy physics. Here, we propose extensions of the conventions of the first SLHA to include various generalisations: the minimal supersymmetric standard model with violation of CP, R-parity, and flavour, as well as the simplest next-to-minimal model.

A light Higgs boson with substantial branching ratio into invisible channels can occur in a variety of models with: light neutralinos, spontaneously broken lepton number, radiatively generated neutrino masses, additional singlet scalar(s) and/or right handed neutrinos in the extra dimensions of TeV scale gravity. We study the observability of the WH and ZH modes at LHC with H decaying invisibly, by carrying out a detailed simulation with two event generators (HERWIG and PYTHIA) and realistic detector simulations (GETJET and CMSJET). We find that the signal with ‘single lepton plus missing ET’ resulting from WH production suffers from a very large background due to the (off-shell) W∗ production via the Drell–Yan process. In contrast, the ZH mode provides a clean signal in the ‘dilepton plus missing ET’ channel. By exploiting this second signature, we show that invisible branching ratios of Higgs bosons, BRinv, larger than ∼0.42 (0.70) can be probed at 5σ level for MH=120 (160) GeV, respectively, assuming an accumulated luminosity of L=100 fb−1.

While the recent discovery of a Higgs-like boson at the LHC is an extremely important and encouraging step towards the discovery of the {\it complete} standard model(SM), the current information on this state does not rule out possibility of beyond standard model (BSM) physics. In fact the current data can still accommodate reasonable values of the branching fractions of the Higgs into a channel with `invisible' decay products, such a channel being also well motivated theoretically. In this study we revisit the possibility of detecting the Higgs in this invisible channel for both choices of the LHC energies, 8 and 14 TeV, for two production channels; vector boson fusion(VBF) and associated production($ZH$). In the latter case we consider decays of the $Z$ boson into a pair of leptons as well as a $b \bar b$ pair. For the VBF channel the sensitivity is found to be more than $5 \sigma$ at both the energies up to an invisible branching ratio ${\cal B}r_{invis} \sim 0.80$, with luminosities $\sim 20/30 {\rm fb}^{-1}$. The sensitivity is further extended to values of ${\cal B}r_{invis} \sim 0.25$ for $300 {\rm fb}^{-1}$ at 14 TeV. However the reach is found to be more modest for the $ZH$ mode with leptonic final state; with about $3.5 \sigma$ for the planned luminosity at 8 TeV, reaching $8 \sigma$ only for 14 TeV for $50 {\rm fb}^{-1}$. In spite of the much larger branching ratio of the $Z$ into a $b \bar b$ channel compared to the dilepton case, the former channel, can provide useful reach upto ${\cal B}r_{invis} \gsim 0.75$, only for the higher luminosity ($300{\rm fb}^{-1}$) option using jet-substructure and jet clustering methods for $b$-jet identification.

We study the allowed parameter space of the constrained minimal supersymmetric Standard Model (cMSSM) in the light of direct searches, constraints from $B$-physics (including the recent measurement of the branching ratio for $B_s \to \mu^+\mu^-$) and the dark matter relic density. For low or moderate values of $\tan\beta$, the strongest constraints are those imposed by direct searches, and therefore, large areas of the parameter space are still allowed. In the large $\tan \beta$ limit, however, the $B$-physics constraints are more restrictive, effectively forcing the squark and gluino masses to lie close to or above a TeV. A light Higgs boson could dramatically change the allowed parameter space, but we need to know its mass precisely for this to be effective. We emphasize that it is still too early to write off the cMSSM, even in the large $\tan\beta$ limit. Finally we explore strategies to extend the LHC search for cMSSM signals beyond the present reach of the ATLAS and CMS Collaborations.

In the context of the minimal supersymmetric extension of the Standard Model, we study the production of Higgs bosons at the large hadron collider via cascade decays of scalar quarks and gluinos. We focus on the cascades involving heavier charginos and neutralinos, which decay into the neutral h, A, H and charged H± bosons and lighter charginos and neutralinos, but we will also discuss direct decays of third-generation squarks into their lighter partners and Higgs bosons as well as top quark decays into H± bosons. We show that the production rates of relatively light Higgs bosons, MΦ≲250 GeV, via these mechanisms can be rather large in some areas of the parameter space. Performing a fast detector simulation analysis that takes into account the signals and the various backgrounds, we show that the detection of the neutral Higgs bosons through their decays into bb̄ pairs, and of the charged Higgs particles through the τ±ν signature, is possible at the LHC.

We have analyzed the prospect of detecting a Higgs signal in mSUGRA/cMSSM based Supersymmetric (SUSY) model via chargino-neutralino ( ${\tilde{\chi}}^{\pm}_{1}\tilde{\chi}^{0}_{2}$ ) production at 8 TeV and 14 TeV LHC energies. The signal is studied in the channel following the decays, ${\tilde{\chi}}^{\pm}_{1} \to W^{\pm} \tilde{\chi}^{0}_{1}$ , $\tilde{\chi}^{0}_{2} \to \tilde{\chi}^{0}_{1} h$ and $h \to b \bar{b}$ . In this analysis reconstruction of the Higgs mass out of two b jets plays a very crucial role in determining the signal to background ratio. We follow two techniques to reconstruct the Higgs mass: (A) adding momenta of two identified b jets, (B) jet substructure technique. In addition, imposing a certain set of selection cuts we observe that the significance is better for the method (B). We find that a signal can be observed for the Higgs mass ∼125 GeV with an integrated luminosity 100 fb−1 for both 8 TeV and 14 TeV LHC energies.

The light singlino-like neutralino is expected to be a promising candidate for DM in the allowed parameter space of the NMSSM. The DM annihilation process takes place via the light Higgs bosons which are natural in this model. Identifying the allowed region of parameter space including various constraints, the detection prospect of such light DM candidate and Higgs bosons are explored at the LHC with its high luminosity options. Light Higgs bosons and the DM candidate, the lightest singlino-like neutralino are indirectly produced at the LHC via the SM Higgs production and its subsequent decays. Jet substructure techniques are used to tag boosted Higgs. It is found that the favourable range of masses of Higgs bosons and neutralino, compatible with a low mass DM solution, can be discovered with a reasonable signal significance ($\sim 5 \sigma$) at the LHC, with the center of mass energy $\sqrt{s}=14$ TeV and integrated luminosity options $\rm{\cal L}=300~fb^{-1}$ and 3000 $\rm fb^{-1}$.

The estimation of the backgrounds for gluino signals in focus point supersymmetry is extended by including the backgrounds from the production of four third generation quarks in the analysis. We find that these backgrounds are negligible if one uses the strong selection criteria proposed in the literature (including this analysis) for heavy gluino searches. Softer selection criteria often recommended for lighter gluino searches yield backgrounds that are small but numerically significant. We have also repeated the more conventional background calculations and compared our results with the other groups. We find that the size of the total residual background estimated by different groups using different event generators and hard kinematical cuts agree approximately. In view of the theoretical uncertainties in the leading order signal and background cross sections mainly due to the choice of the QCD scale, the gluino mass reach at the LHC cannot be pinpointed. However, requiring a signal with ≥3 tagged b-jets (instead of the standard choice of ≥2) it is shown that gluino masses close to 2 TeV can be probed at the LHC for a range of reasonable choices of the QCD scale for an integrated luminosity of 300 fb-1.

Nonuniversal 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 $\ensuremath{\sim}100\text{ }\mathrm{GeV}$, while accommodating the observed Higgs boson mass of $\ensuremath{\sim}125\text{ }\mathrm{GeV}$ 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 dilepton signals. We investigate these signals along with the standard model background for both 8 and 13 TeV LHC runs.

The next-to-minimal supersymmetric Standard Model (NMSSM) with an extended Higgs sector offers at least one Higgs boson as the Standard Model (SM)-like Higgs with a mass around 125 GeV. In this work, we revisit the mass spectrum and couplings of non-SM-like Higgs bosons taking into consideration most relevant constraints and identify the relevant parameter space. The discovery potential of these non-SM-like Higgs bosons, apart from their masses, is guided by their couplings with gauge bosons and fermions which are very much parameter space sensitive. We evaluate the rates of productions of these non-SM-like Higgs bosons at the LHC for a variety of decay channels in the allowed region of the parameter space. Although [Formula: see text], [Formula: see text] modes appear to be the most promising decay channels, but for a substantial region of parameter space the two-photon decay mode has a remarkably large rate. In this study we emphasize that this diphoton mode can be exploited to find the non-SM-like Higgs bosons of the NMSSM and can also be a potential avenue to distinguish the NMSSM from the MSSM. In addition, we discuss briefly the various detectable signals of these non-SM Higgs bosons at the LHC.

In view of the fact that the $n = 1$ Kaluza-Klein (KK) modes in a model with a Universal Extra Dimension (UED), could mimic supersymmetry signatures at the LHC, it is necessary to look for the $n = 2$ KK modes, which have no analogues in supersymmetry. We discuss the possibility of searching for heavy $n = 2$ vector boson resonances -- especially the $g_2$ -- through their decays to a highly-boosted top quark-antiquark pair using recently-developed top-jet tagging techniques in the hadronic channel. It is shown that $t\bar{t}$ signals from the $n = 2$ gluon resonance are as efficient a discovery mode at the LHC as dilepton channels from the $\gamma_2$ and $Z_2$ resonances.

We explore the detection possibility of the light pseudoscalar Higgs boson in the next-to-minimal supersymmetric standard model (NMSSM) at the LHC with the center of mass energy, $\sqrt{S}=13\text{ }\text{ }\mathrm{TeV}$. We focus on the parameter space which provides one of the Higgs bosons as SM-like with a mass of 125 GeV and some of the non-SM-like Higgs bosons can be light having suppressed couplings with fermions and gauge bosons due to their singlet nature. It is observed that for a certain region of model parameter space, the singlet-like light pseudoscalar can decay to the diphoton ($\ensuremath{\gamma}\ensuremath{\gamma}$) channel with a substantial branching ratio. In this study, we consider this diphoton signal of a light pseudoscalar Higgs boson producing it through the chargino-neutralino production and the subsequent decay of the neutralino. We consider the signal consisting of two photons plus missing energy along with a lepton from the chargino decay. Performing a detailed simulation of the signal and backgrounds including detector effects, we present results for a few benchmark points corresponding to the pseudoscalar Higgs boson mass in the range 60--100 GeV. Our studies indicate that some of the benchmark points in the parameter space can be probed with a reasonable significance for $100\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ integrated luminosity. We also conclude that exploiting this channel it is possible to distinguish the NMSSM from the other supersymmetric models.

We reappraise the viability of asymmetric dark matter (ADM) realized as a Dirac fermion coupling dominantly to the Standard Model fermions. Treating the interactions of such a DM particle with quarks/leptons in an effective-interactions framework, we derive updated constraints using mono-jet searches from the Large Hadron Collider (LHC) and mono-photon searches at the Large Electron-Positron (LEP) collider. We carefully model the detectors used in these experiments, which is found to have significant impact. The constraint of efficient annihilation of the symmetric part of the ADM, as well as other observational constraints are synthesized to produce a global picture. Consistent with previous work, we find that ADM with mass in the range $1-100$ GeV is strongly constrained, thus ruling out its best motivated mass range. However, we find that leptophilic ADM remains allowed for $\gtrsim 10$ GeV DM, including bounds from colliders, direct detection, and stellar heating. We forecast that the Future Circular Collider for electron-positron collisions (FCC-ee) will improve sensitivity to DM-lepton interactions by almost an order of magnitude.

We assess the potential of detecting a charged Higgs boson of the MSSM at the LHC via its decays into a chargino and a neutralino. We focus our attention on the region of parameter space with $m_{H^{\pm}} > m_t$ and $3 \lsim tan(beta) \lsim 10$, where identification of the $H^{\pm}$ via other decay modes has proven to be ineffective. Searching for means to plug this hole, we simulate the decays $H^{\pm} --> {\tilde\chi}_1^{\pm} {\tilde\chi}_1^0$ and $H^{\pm} --> {\tilde\chi}_1^{\pm} {\tilde\chi}_2^0, {\tilde\chi}_1^{\pm} {\tilde\chi}_3^0$ --- the former can yield a single hard lepton (from the chargino decay) while the latter can yield three leptons (from the chargino and neutralino decays). Coupled with the dominant top quark + charged Higgs boson production mode, the resulting signature is one or three hard, isolated leptons, substantial missing transverse momentum and a reconstructed (via a 3-jet invariant mass) top quark. The single lepton channel is swamped by background processes; however, with suitable cuts, a trilepton signal emerges. While such a signal suffers from a low number of surviving events (after cuts) and is dependent on several MSSM input parameters (notably $M_2$, $\mu$, and slepton masses), it does fill at least some of the void left by previous investigations.

We investigate the prospects of supersymmetry searches at the LHC with 7 TeV energy. A new set of selection cuts is proposed based on event shapes to control backgrounds. Our preliminary studies show that it is possible to minimize backgrounds to a significantly low level and a conservative estimate suggests that the mass reach can be extended to $\ensuremath{\sim}1.1\text{ }\text{ }\mathrm{TeV}$ for luminosity $\mathcal{L}=1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ with a reasonable signal-to-background ratio.

Machine learning techniques are used for treating jets as images to explore the performance of boosted top quark tagging. Tagging performances are studied in both hadronic and leptonic channels of top quark decay, employing a convolutional neural network (CNN) based technique along with boosted decision trees (BDT). This computer vision approach is also applied to distinguish between left and right polarized top quarks. In this context, an experimentally measurable asymmetry variable is proposed to estimate the polarization. Results indicate that the CNN based classifier is more sensitive to top quark polarization than the standard kinematic variables. It is observed that the overall tagging performance in the leptonic channel is better than the hadronic case, and the former also serves as a better probe for studying polarization.

We study the signature of $H^\pm$ decay into $h^0W$ at the LHC in SUSY models. It has only marginal viability in the MSSM. But in the singlet extensions like the NMSSM one can have a spectacular signature for $H^\pm$ decay into $(h^0,A^0)W$ over a significant domain of parameter space.

We analyze the cascade decays of the scalar quarks and gluinos of the minimal supersymmetric extension of the standard model, which are abundantly produced at the (CERN) Large Hadron Collider, into heavier charginos and neutralinos which then decay into the lighter ones and charged Higgs particles, and we show that they can have substantial branching fractions. The production rates of these Higgs bosons can be much larger than those from the direct production mechanisms, in particular for intermediate values of the parameter $\mathrm{tan}\ensuremath{\beta},$ and could therefore allow for the detection of these particles. We also discuss charged Higgs boson production from direct two-body top and bottom squark decays as well as from two- and three-body gluino decays.

We investigate the prospect of a top squark search at the Fermilab Tevatron run-II in MSUGRA motivated as well as unconstrained supersymmetric models, when the lighter top squark turns out to be the next lightest supersymmetric particle (NLSP). In this case, the decay into a four body final state consisting of a b quark, the lightest neutralino, and two light fermions may compete with the much publicized loop-induced two body decay into a charm quark and the lightest neutralino. We systematically study the parameter space in MSUGRA where the lighter top squark turns out to be the NLSP and calculate the branching ratios of the competing channels in both models. Our results show that the four body decay may indeed be the main discovery channel particularly in the low $\mathrm{tan}\ensuremath{\beta}$ scenarios. We discuss the detectability of top squark pairs in the four body decay channel leading to one lepton $(e$ or $\ensuremath{\mu})$ with two or more jets, accompanied by a large amount of missing energy. We also study the corresponding background processes and the kinematic cuts required to suppress them using parton level Monte Carlo simulations. We comment upon, with illustrative examples, the required revision of the existing mass limits of the top squark NLSP assumed to decay solely into the loop-induced two body channel.

By exploiting the full process p→tH−, in place of the standard Monte Carlo procedure of factorising production and decay, p→t followed by →H−, we show how to improve the discovery reach of the Tevatron (Run 2) in charged Higgs boson searches, in the large tan β region. This is achieved in conjunction with dedicated cuts on a `transverse mass' distribution sensitive to the Higgs boson mass and to `polarisation' effects in the H−→τ−τdecay channel.

The Large Hadron Collider (LHC) has completed its run at 8 TeV with the experiments ATLAS and CMS having collected about $25\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data each. Discovery of a light Higgs boson coupled with lack of evidence for supersymmetry at the LHC so far, has motivated studies of supersymmetry in the context of naturalness with the principal focus being the third generation squarks. In this work, we analyze the prospects of the flavor violating decay mode ${\stackrel{\texttildelow{}}{\mathit{t}}}_{1}\ensuremath{\rightarrow}\mathit{c}{\ensuremath{\chi}}_{1}^{0}$ at 8 and 13 TeV center-of-mass energy at the LHC. This channel is also relevant in the dark matter context for the stop-coannihilation scenario, where the relic density depends on the mass difference between the lighter stop quark (${\stackrel{\texttildelow{}}{t}}_{1}$) and the lightest neutralino (${\ensuremath{\chi}}_{1}^{0}$) states. This channel is extremely challenging to probe, especially for situations when the mass difference between the lighter stop quark and the lightest neutralino is small. Using certain kinematical properties of signal events we find that the level of backgrounds can be reduced substantially. We find that the prospect for this channel is limited due to the low production cross section for top squarks and limited luminosity at 8 TeV, but at the 13 TeV LHC with $100\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ luminosity, it is possible to probe top squarks with masses up to $\ensuremath{\sim}450\text{ }\text{ }\mathrm{GeV}$. We also discuss how the sensitivity could be significantly improved by tagging charm jets.

Tight limits are derived on models with extended Higgs sectors, including the minimal supersymmetric standard model (MSSM), by exploiting the data on ${\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}+2$ jets final states, used by the CDF Collaboration to place limits on third generation leptoquarks. The main observation here is that both leptoquark production and associated $b\overline{b}$ Higgs production can lead to $b\overline{b}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$ final states. For the MSSM we find that $\mathrm{CP}$-odd neutral Higgs boson masses up to 190 GeV are excluded if the ratio of vacuum expectation values $\mathrm{tan}\ensuremath{\beta}$ is 50.

The minimal supergravity model predicts the polarization of the tau coming from the stau to bino decay in the co-annihilation region to be $+1$. This can be exploited to extract this soft tau signal at LHC and also to measure the tiny mass differences between the stau and the bino lightest superparticle. Moreover, this strategy will be applicable for a wider class of bino lightest superparticle models, where the lighter stau has a right component at least of similar size as the left.

The occurrence of a significant amount of supersymmetric lepton flavour violation at laboratory energies, through $\tilde\nu_\mu - \tilde\nu_\tau$ mixing, has become a realistic possibility in the wake of the super-Kamiokande atmospheric neutrino result. This effect can be observed in an e+e- linear collider with the distinct final state tau+mu+ jets+E_T. We show that the pair production of charginos can make an important contribution to this process and has to be taken into account in addition to that of sneutrinos or charged sleptons. Some case studies are presented with CM energies of 500 and 800 GeV and integrated luminosities of 50, 500 and 1000 fb-1.

In many SUSY models the first SUSY signal in the proposed International Linear Collider is expected to come from the pair production of $\tilde\tau_1$, followed by its decay into $\tau$+LSP. We study a simple and robust method of measuring the polarization of this $\tau$ in its 1-prong hadronic decay channel,and show how it can be used to discriminate between SUSY models and to determine SUSY parameters.

A bstract We explore a possible signal of the presence of relatively light electroweakinos (ewinos) and a singlet-like scalar ( a S ) of the Z 3 -symmetric Next-to-Minimal Supersymmetric Standard Model ( Z 3 -NMSSM) in the cascade decays of not so heavy top squarks ( $$ {m}_{{\tilde{t}}_1} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>m</mml:mi> <mml:msub> <mml:mover> <mml:mi>t</mml:mi> <mml:mo>~</mml:mo> </mml:mover> <mml:mn>1</mml:mn> </mml:msub> </mml:msub> </mml:math> ≲ 1 . 5 TeV) that may be produced in pairs at the Large Hadron Collider LHC. We work in a scenario where the lightest (next-to-lightest) SUSY particle is bino (singlino)-like with its mass below 100 GeV and is mildly tempered with higgsino and singlino admixtures. The singlet-like scalar provides an annihilation funnel for the bino-like states such that the latter could act as a viable dark matter candidate, unlike what is now highly constrained in the MSSM. We consider a pair of immediately heavier neutralinos and the lighter chargino which all are higgsino-like with masses in the range ~ 0 . 5–1 TeV and are still compatible with all experimental constraints. While these states may not be accessible in their direct searches at the LHC in our present scenario, such ewinos could still be traced in the decays of the top squarks of the above-mentioned kind. We consider the signal final state "Image missing"<!-- image only, no MathML or LaTex --> at the LHC. We find that while a usual cut-based analysis (CBA) of LHC data worth 300 fb − 1 would be unable to discover such excitations, a multivariate analysis (MVA) can be reasonably sensitive to higgsino-like ewinos having masses ≳ 650 GeV when $$ {m}_{{\tilde{t}}_1} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>m</mml:mi> <mml:msub> <mml:mover> <mml:mi>t</mml:mi> <mml:mo>~</mml:mo> </mml:mover> <mml:mn>1</mml:mn> </mml:msub> </mml:msub> </mml:math> ≳ 1 TeV. On the other hand, with 3000 fb − 1 of data, these masses become accessible in a CBA while even an MVA on such a data set is unlikely to find these ewinos with masses around 1 TeV when $$ {m}_{{\tilde{t}}_1} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>m</mml:mi> <mml:msub> <mml:mover> <mml:mi>t</mml:mi> <mml:mo>~</mml:mo> </mml:mover> <mml:mn>1</mml:mn> </mml:msub> </mml:msub> </mml:math> hits ∼ 1 . 5 TeV.

In minimal supergravity based supersymmetry models the charged sleptons as well as the sneutrinos may be lighter than the squarks. In such light slepton scenario the search for lighter stop squark has been investigated in the dilepton + missing $p_T(\missingpt)$ +jets ($\ge 1$) channel at Tevatron. In this scenario semileptonic decay of lighter stop squark has been considered via off shell and on shell charginos. In the latter case the chargino undergoes pure leptonic 2-body decay. We observe that for some favourable region of the MSSM parameter space one can probe lighter stop squark mass upto 140 GeV with few events in the present data set for which the luminosity is 110 pb$^{-1}$. At the MI upgrade one is likely to end up with more events.

In top quark production, the polarization of top quarks, decided by the chiral structure of couplings, is likely to be modified in the presence of any new physics contribution to the production. Hence, it is a good discriminator for those new physics models wherein the couplings have a chiral structure different than that in the Standard Model. In this paper, we construct probes of the polarization of a top quark decaying hadronically, using easily accessible kinematic variables such as the energy fraction or angular correlations of the decay products. Tagging the boosted top quark using the jet substructure technique, we study the robustness of these observables for a benchmark process, ${W}^{\ensuremath{'}}\ensuremath{\rightarrow}tb$. We demonstrate that the energy fraction of $b$ jet in the laboratory frame and a new angular variable, constructed by us in the top rest frame, are both very powerful tools to discriminate between the left and right polarized top quarks. Based on the polarization-sensitive angular variables, we construct asymmetries that reflect the polarization. We study the efficacy of these variables for two new physics processes that give rise to boosted top quarks: (i) the decay of the top squark in the context of supersymmetry searches and (ii) decays of the Kaluza-Klein (KK) graviton and KK gluon, in the Randall-Sundrum model. Remarkably, it is found that the asymmetry can vary over a wide range about $+20%$ to $\ensuremath{-}20%$. The dependence of asymmetry on top quark couplings of the new particles present in these models beyond the SM is also investigated in detail.

The like sign dileptons provide the most promising signature for superparticle search in a large category of $R$-parity violating SUSY models. We estimate the like sign dilepton signals at the Tevatron collider, predicted by these models, over a wide region of the MSSM parameter space. One expects an unambiguous signal upto a gluino mass of $200 - 300$ GeV ($\geq 500$ GeV) with the present (proposed) accumulated luminosity of $\sim 0.1~(1)~{\rm fb}^{-1}$.

It is shown that if the sneutrino is the second lightest SUSY particle, then the decay products of squarks and gluinos produced at the TEVATRON collider tend to have i) more leptons, ii) smaller number of jets and iii) two or more carriers of . This may relax the existing limits on the squark and gluino masses. This effect is likely to be even more striking as these limits improve with accumulation of data. Numerical results for signal cross sections are presented and compared with the ones obtained without a light sneutrino. The possibilities of accommodating this scenario in models motivated by N = 1 SUGRA are discussed.

We have revisited the prospects of supersymmetry searches at the LHC with 7 TeV energy along with the prediction of the discovery potential at 8 TeV energy assuming an integrated luminosity $5\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ and $20\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ with minimal supergravity/minimal supersymmetric standard model as a model framework. We discuss further optimization of our selection strategy, which is based on the hadronic event shape variables. Evaluating the standard model backgrounds and signal rates in detail, we predict the discovery reach in the ${m}_{0}\ensuremath{-}{m}_{1/2}$ plane for 7 TeV with $5\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ luminosity. We also present the discovery reach for 8 TeV energy with an integrated luminosity $5\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ and $20\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. A comparison is made between our results and the exclusion plots obtained by CMS and ATLAS. Finally, discovery reach in the gluino and squark mass plane at the 7 TeV and 8 TeV energy is also presented.

We have analyzed the prospect of probing a nonuniversal gaugino mass model of mixed bino-Higgsino dark matter at the current 7 TeV run of LHC. It provides cosmologically compatible dark matter relic density over two broad bands of parameters, corresponding to ${m}_{\stackrel{\texttildelow{}}{g}}&lt;{m}_{\stackrel{\texttildelow{}}{q}}$ and ${m}_{\stackrel{\texttildelow{}}{g}}\ensuremath{\sim}{m}_{\stackrel{\texttildelow{}}{q}}$. The supersymmetry spectrum of this model has two distinctive features: (i) an approximate degeneracy among the lighter chargino and neutralino masses, and (ii) an inverted mass hierarchy of squark masses. We find that these features can be exploited to obtain a viable signal up to ${m}_{\stackrel{\texttildelow{}}{g}}\ensuremath{\sim}800\text{ }\text{ }\mathrm{GeV}$ over both the parameter bands with an integrated luminosity $5\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$.

The top quark data in the lepton plus $\ensuremath{\tau}$ channel offers a viable probe for the charged Higgs boson signal. We analyze the recent Collider Detector at Fermilab data in this channel to obtain a significant limit on the ${H}^{\ifmmode\pm\else\textpm\fi{}}$ mass in the large $\mathrm{tan}\ensuremath{\beta}$ region.

In the minimal SUGRA model the lighter tau slepton is expected to be the second lightest superparticle over a large parameter range at large tanβ. Consequently one expects a viable SUGRA signal at LHC in the tau lepton channel coming from the decay of these tau sleptons. The model predicts the polarization of this tau lepton to be +1 to a very good accuracy. We show how this prediction can be tested by looking at the momentum fraction of the tau-jet, carried by the charged prong, in its 1-prong hadronic decay channel.

We have done a fast simulation analysis of the H± signal at LHC in 1 and 3 prong hadronic τ-jet channels along with a tt̄ background. The τ polarization was effectively used to suppress the background in both channels. Combining this with appropriate cuts on pT of the τ-jet, the missing ET and the azimuthal angle between them reduces the background below the signal level. Consequently, one gets a viable H± signal up to a mass range of 600–700 GeV at moderate to large tanβ.

Signature of heavier charged Higgs boson, much above the top quark mass, is investigated at the LHC Run 2 experiments, following its decay mode via top and bottom quark focusing on both hadronic and leptonic signal final states. The generic two Higgs doublet model framework is considered with a special emphasis on supersymmetry motivated Type II model. The signal is found to heavily affected by the huge irreducible backgrounds due to the top pair production and QCD events. The jet substructure technique is used to tag moderately boosted top jets in order to reconstruct charged Higgs mass. The simple cut based analysis is performed optimizing various kinematic selections, and the signal sensitivity is found to be reasonable for only lower range of charged Higgs masses for very high luminosity 3000 fb$^{-1}$ option. However, employing the multi-variate analysis(MVA) technique, a remarkable improvement in signal sensitivity is achieved. We find, the charged Higgs signal for the mass range about $300-600$ is observable with 1000 fb$^{-1}$ luminosity option. However, for more high luminosity option 3000 fb$^{-1}$, the discovery potential can be extended to $700-800$ GeV.

Top squark contributions to the radiative correction to ${R}_{b}$ and the top quark decay are analyzed over the relevant MSSM parameter space. One sees a 30% increase in the former along with a similar drop in the latter in going from the Higgsino-dominated to the mixed region. Consequently, one can get a viable SUSY contribution to ${R}_{b}$ within the constraint of the top quark data only in the mixed region, corresponding to a photino-dominated LSP. We discuss the phenomenological implications of this model for top quark decay and direct top squark production, which can be tested with the Fermilab Tevatron data.

The signal of a lighter top squark has been looked at for using Fermilab Tevatron data in the dielectron plus dijet channel. We find that the mass of the lighter top squark when it decays dominantly in the electron plus jet channel can be ruled out up to 220 GeV at 95% C.L. using dielectron data. In the framework of the R-parity breaking supersymmetry (SUSY) model we exclude relevant R-parity violating couplings for a range of top squark masses and other SUSY parameters. The bounds on R-parity violating couplings are very stringent for the parameter space where the lighter top squark turns out to be the next to lightest supersymmetric particle.

We have estimated the limiting branching ratio of the R-parity violating (RPV) decay of the lighter top squark, $\tilde t_1 \ar l^+ d$ ($l=e$ or $\mu $ and d is a down type quark of any flavor), as a function of top squark mass($\MST$) for an observable signal in the di-lepton plus di-jet channel at the Tevatron RUN-II experiment with 2 fb$^{-1}$ luminosity. Our simulations indicate that the lepton number violating nature of the underlying decay dynamics can be confirmed via the reconstruction of $\MST$. The above decay is interesting in the context of RPV models of neutrino mass where the RPV couplings ($\lambda'_{i3j}$) driving the above decay are constrained to be small ($\lsim 10^{-3} - 10^{-4} $). If $\tilde t_1$ is the next lightest super particle - a theoretically well motivated scenario - then the RPV decay can naturally compete with the R-parity conserving (RPC) modes which also have suppressed widths. The model independent limiting BR can delineate the parameter space in specific supersymmetric models, where the dominating RPV decay is observable and predict the minimum magnitude of the RPV coupling that will be sensitive to Run-II data. We have found it to be in the same ballpark value required by models of neutrino mass, for a wide range of $\MST$. A comprehensive future strategy for linking top squark decays with models of neutrino mass is sketched.

The dimuon plus dijet signal is analyzed in the top squark pair production at Tevatron Run-II experiment and the total event rate is compared with the existing dimuon data. This comparison rules out top squark mass upto 188(104) GeV for the branching fraction 100%(50%) of top squark decay into the muon plus quark via lepton number violating coupling. Interpretation of this limit in the framework of R-parity violating(RPV) SUSY model puts limit on relevant RPV coupling for a given top squark mass and other supersymmetric model parameters. If $\MST \lsim 180$ GeV we found that the RPV couplings are roughly restricted to be within $\sim 10^{-4}$ which is at the same ballpark value obtained from the neutrino data. The limits are very stringent for a scenario where top squarks appear to be the next lightest supersymmetric particles.

The discovery potential of light pseudo scalar Higgs boson for the mass range 10-60 GeV is explored. In the context of the next-to-minimal supersymmetric standard(NMSSM) model, the branching fraction of light pseudo scalar Higgs boson decaying to a pair of photon can be quite large. A pair of light pseudo scalar Higgs boson produced indirectly through the standard model Higgs boson decay yields multiple photons in the final state and the corresponding production rate is restricted by ATLAS data. Discussing the impact of this constraint in the NMSSM, the detection prospects of light pseudoscalar Higgs boson in the channel consisting of at least three photons, a lepton and missing transverse energy are reported. It is observed that the possibilities of finding the pseudoscalar Higgs boson for the above mass range are promising for an integrated luminosity $\mathcal{L}=100 \text{fb}^{-1}$ with moderate significances, which can reach to more than 5$\sigma$ for higher luminosity options.

We have analyzed the supersymmetric tri-lepton signals for sparticle searches at the Tevatron in the minimal supersymmetric standard model with general CP phases without generational mixing. The CP phases may affect very strongly the chargino and neutralino mass spectrums and $\sigma(p\bar{p}\to\tilde{\chi}^-_1\tilde{\chi}^0_2)$ as well as ${\cal B}(\tilde{\chi}^-_1\to\tilde{\chi}^0_1\ell^-\nu)$ and ${\cal B}(\tilde{\chi}^0_2\to\tilde{\chi}^0_1\ell^+\ell^-)$. Even under the stringent constraints from the electron electric dipole moment the CP phases can lead to a minimum of the tri-lepton event rate for their non-trivial values.

The lightest neutralino, assumed to be the lightest supersymmetric particle, is proposed to be a dark matter (DM) candidate for the mass $\mathcal{O}(100)\text{ }\text{ }\mathrm{GeV}$. Constraints from various direct dark matter detection experiments and Planck measurements exclude a substantial region of parameter space of minimal supersymmetric standard model. However, a ``mild-tempered'' neutralino with dominant bino composition and a little admixture of Higgsino is found to be a viable candidate for DM. Within the minimal supersymmetric standard model framework, we revisit the allowed region of parameter space that is consistent with all existing constraints. Regions of parameters that are not sensitive to direct detection experiments, known as ``blind spots,'' are also revisited. Complimentary to the direct detection of DM particles, a mild-tempered neutralino scenario is explored at the LHC with the center of mass energy $\sqrt{\mathrm{s}}=13\text{ }\text{ }\mathrm{TeV}$ through the top-squark pair production, and its subsequent decays with the standard-model-like Higgs boson in the final state. Our considered channel is found to be very sensitive also to the blind spot scenario. Detectable signal sensitivities are achieved using the cut-based method for the high luminosity options 300 and $3000\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$, which are further improved by applying the multivariate analysis technique.

The most promising source of SUGRA signal at the Tevatron collider is the pair-production of electroweak gauginos, followed by their leptonic decay. In the parameter range corresponding to dominant leptonic decay of these gauginos one or more of the leptons are expected to be $\tau$ with $P_\tau \simeq +1$. This polarization can be effectively used to distinguish the signal from the background in the 1-prong hadronic decay channel of $\tau$ by looking at the fractional $\tau$-jet momentum carried by the charged prong.

Boosted top quark tagging is one of the challenging, and at the same time exciting, tasks in high energy physics experiments, in particular in the exploration of new physics signals at the LHC. Several techniques have already been developed to tag a boosted top quark in its hadronic decay channel. Recently tagging the same in the semi-leptonic channel has begun to receive a lot of attention. In the current study, we develop a methodology to tag a boosted top quark ($p_T&gt;$ 200 GeV) in its semi-leptonic decay channel with a $τ$-lepton in the final state. In this analysis, the constituents of the top fatjet are reclustered using jet substructure technique to obtain the subjets, and then $b$- and $τ$- like subjets are identified by applying standard $b$- and $τ$-jet identification algorithms. We show that the dominant QCD background can be rejected effectively using several kinematic variables of these subjects, such as energy sharing among the jets, invariant mass, transverse mass, Nsubjettiness etc., leading to high signal tagging efficiencies. We further assess possible improvements in the results by employing multivariate analysis techniques. We find that using this proposed top-tagger, a signal efficiency of $\sim 77\%$ against a background efficiency of $\sim 3\%$ can be achieved. We also extend the proposed top-tagger to the case of polarized top quarks by introducing a few additional observables calculated in the rest frame of the $b-τ$ system. We comment on how the same methodology will be useful for tagging a boosted heavy BSM particle with a $b$ and $τ$ in the final state.

Boosted top quark tagging is one of the challenging, and at the same time exciting, tasks in high energy physics experiments, in particular in the exploration of new physics signals at the LHC. Several techniques have already been developed to tag a boosted top quark in its hadronic decay channel. Recently tagging the same in the semileptonic channel has begun to receive a lot of attention. In the current study, we develop a methodology to tag a boosted top quark (${p}_{T}&gt;200\text{ }\text{ }\mathrm{GeV}$) in its semileptonic decay channel with a $\ensuremath{\tau}$-lepton in the final state. In this analysis, the constituents of the top fatjet are reclustered using jet substructure technique to obtain the subjets, and then $b$- and $\ensuremath{\tau}$- like subjets are identified by applying standard $b$- and $\ensuremath{\tau}$-jet identification algorithms. We show that the dominant QCD background can be rejected effectively using several kinematic variables of these subjects, such as energy sharing among the jets, invariant mass, transverse mass, $N$-subjettiness etc., leading to high signal tagging efficiencies. We further assess possible improvements in the results by employing multivariate analysis techniques. We find that using this proposed top-tagger, a signal efficiency of $\ensuremath{\sim}77%$ against a background efficiency of $\ensuremath{\sim}3%$ can be achieved. We also extend the proposed top-tagger to the case of polarized top quarks by introducing a few additional observables calculated in the rest frame of the $b\ensuremath{-}\ensuremath{\tau}$ system. We comment on how the same methodology will be useful for tagging a boosted heavy BSM particle with a $b$ and $\ensuremath{\tau}$ in the final state.

A bstract We study the top-quark production along with a Higgs boson and a jet (tHq) at the LHC experiment within the framework of the Standard Model Effective Field Theory (SMEFT). A strategy is developed to constrain the Wilson Coefficients (WC) corresponding to the associated SMEFT operators using the latest LHC measurements. The best-fit values of these WCs are presented. Finally, we demonstrate the feasibility of finding the effects of these operators on various kinematical observables of the tHq process at the LHC. We find that for a set of best-fitted values of the considered WCs, the excess of signal over the backgrounds can be achieved with a reasonable significance at the center of mass energy $$ \sqrt{s} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math> = 13 TeV and for integrated luminosity options $$ \mathcal{L} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>L</mml:mi> </mml:math> =300 fb − 1 and 3000 fb − 1 .

This is a summary of the projects undertaken by the working group I on high energy and collider physics.

The т polarisation can be easily measured at the LHC in the 1-prong hadronic т decay channel by measuring what fraction of the т-jet momentum is carried by the charged track. A simple cut requiring this fraction to be τ; 0.8 retains most of the P т=+1 т -jet signal while suppressing the P т=−1 т-jet background and practically eliminating the fake t background. This can be utilised to extract the charged Higgs signal. It can be also utilised to extract the SUSY signal in the stau NLSP region, and in particular the stau co-annihilaton region.

We consider models of supersymmetry which can incorporate sizeable mixing between different generations of sfermions. While the mixing is constrained by the non-observation of various flavour changing neutral current (FCNC) processes, there exist regions of SUSY parameter space where the effects of such mixing can be probed at colliders. In this work, we explore this possibility by focussing on the slepton sector. The sleptons are produced through cascade decays in direct neutralino-chargino ($\chi_2^0\chi_1^\pm$) pair production at the LHC. The final state is characterized by 3 leptons and missing energy. We probe the lepton flavour violating (LFV) vertex originating from $\chi_2^0$ decay and identify a distinct and unambiguous combination of the tri-lepton final state which include a lepton pair with same flavour and same sign (SFSS) in addition to a pair with opposite flavour and opposite sign (OFOS). This combination of tri-lepton final state containing both OFOS and SFSS pairs, can not only suppress the SM background but can also differentiate the flavour violating decays of $\chi_2^0$ from its corresponding flavour conserving decays. We present results for various signal benchmark points taking into account background contributions assuming two luminosity options (100 fb$^{-1}$ and 1000 fb$^{-1}$) for LHC Run 2 experiment.

Relatively light sneutrinos which are experimentally allowed and are not theoretically disfavoured may significantly affect the currently popular search strategies for supersymmetric particles by decaying dominantly into an invisible channel. In certain cases the second lightest neutralino may also decay invisibly leading to two extra carriers of missing energy (in addition to the lightest supersymmetric particle (LSP) ) - the virtual LSPs (VLSPs). The lighter charginos which would be produced in pairs with reasonably large cross-sections at TEVATRON energies, decay dominantly into the hadronically quiet lepton + sneutrino ($\not{E_T}$ ) modes with large branching ratios leading to interesting unlike sign dilepton events which are not swamped by the standard model background. The kinematical cuts required to eliminate the backgrounds from WW, Drell-Yan and $\tau$ pair production are discussed in detail. With 100 $pb^{-1}$ luminosity 10 - 35 background free events can be found in a large region of the SUSY parameter space.

The favored $R$-parity-violating SUSY scenarios for the anomalous DESY HERA events correspond to top and charm squark production via the ${\ensuremath{\lambda}}_{131}^{\ensuremath{'}}$ and ${\ensuremath{\lambda}}_{121}^{\ensuremath{'}}$ couplings. In both cases the corresponding electronic branching fractions of the squarks are expected to be $\ensuremath{\ll}1$. Consequently the canonical leptoquark signature is incapable of probing these scenarios at the Fermilab Tevatron collider over most of the MSSM parameter space. We suggest alternative signatures for probing them at Tevatron, which seem to be viable over the entire range of MSSM parameters.

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 dilepton signals. We investigate these signals along with the standard model background for both 8 and 13 TeV LHC runs.

The Large Hadron Collider (LHC) experiment has successfully completed data taking at center of mass (COM) energy 7 TeV in 2011 and very recently for 8 TeV. Measurement of cross sections predicted by the standard model were the main tasks in the beginning. The inclusive jet cross section and dijet mass measurement is already done at 7 TeV energy by Compact Muon Solenoid (CMS) detector with integrated luminosity 5 fb$^{-1}$. In these measurement one needs to understand and measure precisely the kinematic properties of jets which involve many theoretical and experimental issues. The goal of this article is to discuss all these issues including jet measurements in CMS and subsequently review the inclusive jet cross section and dijet mass measurement in CMS at 7 TeV with integrated luminosity 5 fb$^{-1}$. The measurements, after unfolding the data, are also compared with the next leading order (NLO) theory predictions, corrected for the non-perturbative (NP) effects, for five different sets of parton distribution functions (PDF). It is observed that the measurements, for both cases, agree with the theory prediction within $\sim$8-10% depending on transverse momentum ($p_T$) and dijet invariant mass ($M_{jj}$) of jets.

In some extensions of the standard model with extended Higgs sectors, events from new particle production may pass the selection criteria for Higgs search in different channels at the LHC---14 TeV and mimic Higgs signals. This intriguing possibility is illustrated by PYTHIA based simulations using several representative points in the parameter space of the minimal supersymmetric standard model (MSSM) including a point in the minimal supergravity model consistent with the dark matter (DM) relic density data. Our simulations explore the interplay between the charged Higgs signal and typical squark-gluino events. We argue that the standard selections like the one based on the polarization properties of the $\ensuremath{\tau}$'s from charged Higgs decay, though adequate for handling the SM backgrounds, may not be very efficient in the presence of SUSY backgrounds. We then propose an alternative search strategy based on pure kinematics which sufficiently controls both the SM and the MSSM backgrounds. For charged Higgs masses (${H}^{\ifmmode\pm\else\textpm\fi{}}$) in the deep decoupling regime ($600\text{ }\text{ }\mathrm{GeV}\ensuremath{\lesssim}{m}_{{H}^{\ifmmode\pm\else\textpm\fi{}}}\ensuremath{\lesssim}800\text{ }\text{ }\mathrm{GeV}$) this method works well and extends the LHC reach close to 800 GeV for an integrated luminosity of $30\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ with or without the SUSY background. For a lighter charged Higgs a judicious combination of the old selections and some of the cuts proposed by us may disentangle the Higgs signal from the squark-gluino backgrounds quite effectively.

Machine learning techniques are used to explore the performance of boosted top quark tagging, treating jets as images.Tagging performances are studied in both hadronic and leptonic channels, employing a convolutional neutral network (CNN) based technique along with boosted decision trees (BDT).This computer vision approach is also applied to distinguish between left and right polarized top quarks, and an experimentally measurable asymmetry variable is constructed to estimate the polarization.Results indicates that the CNN based classifier is more sensitive to top quark polarization than the standard kinematic variables.It is observed that the overall tagging performance in the leptonic channel is better than the hadronic case, and the former also serves as a better probe for studying polarization.

The CMS hadron calorimeter is a sampling calorimeter with brass absorber and plastic scintillator tiles with wavelength shifting fibres for carrying the light to the readout device. The barrel hadron calorimeter is complemented with a outer calorimeter to ensure high energy shower containment in CMS and thus working as a tail catcher. Fabrication, testing and calibrations of the outer hadron calorimeter are carried out keeping in mind its importance in the energy measurement of jets in view of linearity and resolution. It will provide a net improvement in missing measurements at LHC energies. The outer hadron calorimeter has a very good signal to background ratio even for a minimum ionising particle and can hence be used in coincidence with the Resistive Plate Chambers of the CMS detector for the muon trigger.

The parton distribution functions (PDFs) of the proton are one of the essential ingredients to describe physics processes at hadron colliders. The $Z$ boson production data at the LHC have a potential to constrain PDFs, especially the gluon distribution. In this study the CMS measurement of the inclusive double differential $Z$ boson production cross section in terms of transverse momentum and rapidity is compared to the next-to-leading order theory predictions at the center-of-mass energy, $\sqrt{s}=8\text{ }\text{ }\mathrm{TeV}$ with an integrated luminosity of $19.71\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. In addition, the sensitivity of this measurement to PDFs is studied within the framework of the HERAFitter. A moderate improvement to the gluon distribution is observed at the Bjorken $x\ensuremath{\approx}0.1$ region. However, in order to obtain further improvement to the gluon distribution in the global fits, the higher-order theory calculations accessible via fast techniques are necessary.

Transverse momentum spectra of vector bosons in Drell-Yan events have always been interesting observables since they test the theoretical description of the process. At lower end the spectrum tests the model of underlying event while the high tail can be compared with predictions from perturbative QCD. However the measurements at LHC are limited due to the resolution in the measurement of momenta of the daughter leptons, electron and muon, in particular. A novel variable phistar has been proposed recently which uses the angular correlation of the lepton pairs from Z decay to probe the transverse momenta the vector boson and hence has less systematic error.

We study the top-quark production along with a Higgs boson and a jet (tHq) at the LHC experiment within the framework of the Standard Model Effective Field Theory (SMEFT). A strategy is developed to constrain the Wilson Coefficients (WC) corresponding to the associated SMEFT operators using the latest LHC measurements. The best-fit values of these WCs are presented. Finally, we demonstrate the feasibility of finding the effects of these operators on various kinematical observables of the tHq process at the LHC. We find that for a set of best-fitted values of the considered WCs, the excess of signal over the backgrounds can be achieved with a reasonable significance at the center of mass energy $\sqrt{s}=13$ TeV and for integrated luminosity options ${\cal L}=$300 $\rm fb^{-1}$ and 3000 $\rm fb^{-1}$.

We study the prospects of a simultaneous hunt at the Large Hadron Collider (LHC) of relatively light electroweakinos and a singlet-like scalar of the $Z_3$-symmetric Next-to-Minimal Supersymmetric Standard Model ($Z_3$-NMSSM) in the cascade decays of not so heavy ($\lesssim 1.5$ TeV) top squarks that are produced in pairs at the LHC which characteristically involve the singlet-like states. We work in a scenario where the lightest (next-to-lightest) SUSY particle is bino (singlino)-like with a mass below 100 GeV ($\gtrsim 100$ GeV), whereas a pair of immediately heavier neutralinos and the lighter chargino are higgsino-like with masses in the range $\sim 500$ GeV -- 1 TeV. Further, the singlet-like scalar present in the spectrum provides a funnel for a rapid enough mutual annihilation of the LSP thus making the latter meet the experimental upper bound on its relic abundance. The scenario is motivated by its ability to offer a bino-like dark matter with such a mass unlike what is now disfavored in the MSSM while avoiding the stringent lower bounds from the LHC experiments on the masses of these involved particles and still remaining reasonably `natural'. We find that while a usual cut-based analysis (CBA) on LHC data worth 300 $\text{fb}^{-1}$ would be unable to discover such excitations, a multivariate analysis (MVA) can be reasonably sensitive to higgsino-like electroweakinos having masses $\gtrsim 650$ GeV when the lighter top squark has a mass $\gtrsim 1$ TeV. On the other hand, with 3000 $\text{fb}^{-1}$ of data these masses become accessible in a CBA while even an MVA on such a data set is unlikely to find these electroweakinos with masses around 1 TeV when the mass of the lighter top squark hits $\sim 1.5$ TeV.

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 $\Lambda$. 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. The best-fit values of these WCs are presented. Finally, we discuss the discovery potential of the signatures of those operators. We find that a discoverable excess due to SMEFT effects can be observed in the tHq process at the LHC with the center of mass energy $\sqrt{s}=13$ TeV and integrated luminosity options ${\cal L}=$300 $\rm fb^{-1}$ and 3000 $\rm fb^{-1}$.

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

The light singlino-like neutralino is expected to be a promising candidate for dark matter(DM) in the allowed parameter space of the next-to-minimal supersymmetric standard model(NMSSM). The DM annihilation process takes place via the light Higgs bosons which are natural in this model. Identifying the allowed region of parameter space including various constraints, we present here, the detection prospect of such light DM candidate and Higgs bosons at the LHC. It is found that the range of Higgs bosons and neutralino masses compatible with a low mass DM solution can be discovered at the LHC with the center of mass energy $$\sqrt{s}=14$$ TeV with a reasonable signal significance ( $${\sim }5 \sigma $$ ) corresponding to integrated luminosity options 300 and 3000 $$\textrm{fb}^{-1}$$ .

This is a summary of the beyond the Standard Model (including model building) working group of the WHEPP-X workshop held at Chennai from January 3 to 15, 2008.

Signature of heavier charged Higgs boson, much above the top quark mass, is investigated at the LHC Run 2 experiments, following its decay mode via top and bottom quark focusing on both hadronic and semi-leptonic signal final states in the context of generic two Higgs doublet model with a special emphasis on supersymmetry motivated Type II model.The signal is found to be heavily affected by huge irreducible standard model backgrounds due to the top quark pair production and QCD events.The jet substructure technique is used to tag moderately boosted top jets in order to reconstruct charged Higgs mass.The simple cut based analysis shows very poor sensitivity.However, employing the multi-variate analysis(MVA) technique, a remarkable improvement in signal sensitivity is achieved.We find that the charged Higgs signal for the mass range about 300 -600 GeV is observable with 1000 fb -1 luminosity.However, for high luminosity, L = 3000fb -1 , the discovery potential can be extended to 700 -800 GeV.

We illustrate preliminary results obtained through Monte Carlo (HERWIG) and detector (ATLFAST) simulations of the $H^\pm\toτ^\pmν_τ$ signature of charged Higgs bosons with masses comparable to that of the top quark.

We have done a fast simulation analysis of the charged Higgs signal at LHC in the 1 and 3 prong hadronic $τ$-jet channels along with the $t \bar t$ background. The $τ$ polarization was effectively used to suppress the background in both the channels. Combining this with appropriate cuts on the $p_T$ of the $τ$-jet, the missing $E_T$ and the azimuthal angle between them reduces the background below the signal level. Consequently one gets a viable charged higgs signal up to a mass range of 600-700 GeV at moderate to large $\tanβ$.

Supersymmetric (SUSY) spectrum generators, decay packages, Monte-Carlo programs, dark matter evaluators, and SUSY fitting programs often need to communicate in the process of an analysis. The SUSY Les Houches Accord provides a common interface that conveys spectral and decay information between the various packages. Here, we propose extensions of the conventions of the first SUSY Les Houches Accord to include various generalizations: violation of CP, R-parity and flavor as well as the simplest next-to-minimal supersymmetric standard model (NMSSM).

I report here on the systematic analysis at Tevatron of the R-parity violating SUSY signals which correspond to the possible solution of anomalous HERA events.

Relatively light sneutrinos, which are experimentally allowed, may significantly affect the currently popular search strategies for supersymmetric particles by decaying dominantly into an invisible channel. In certain cases the second lightest neutralino may also decay invisibly leading to two extra carriers of missing energy -- in addition to the lightest supersymmetric particle (LSP) \zi\ -- the virtual LSPs (VLSPs). It is shown that these VLSPs are allowed in supergravity models with common scalar and gaugino masses at the unification scale for a sizable region of parameter space and are consistent with all constraints derived so far from SUSY searches. The pair production of right handed sleptons, which can very well be the lightest charged SUSY particles in this scenario, at LEP 200 and their decay signatures are discussed. The signal survives kinematical cuts required to remove the standard model background. Charginos are also pair produced copiously if kinematically accessible; they also decay dominantly into hadronically quiet di--lepton + \etmiss\ modes leading to interesting unlike sign dilepton events which are again easily separable from the Standard Model backgrounds at LEP 200 energies.