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Ushoshi Maitra

Publications and source records attributed to Ushoshi Maitra.

10 recordsLinked to original sources

Pinning down Anomalous $WWγ$ Couplings at the LHC

We make a careful analysis of $W^\pmγ$ production at the LHC, identifying the $W^\pm$ through leptonic decays, with a view to exploring the sensitivity of the machine to anomalous $CP$-conserving $WWγ$ interactions. All the available kinematic variables are used, but we find that the most useful one is the opening angle in the transverse plane between the decay products of the $W^\pm$. It is shown that even a simple-minded analysis using this variable can lead to a much greater sensitivity at the LHC than the current constraints on the relevant parameters.

hep-ph

Discovery prospects of a light Higgs boson at the LHC in type-I 2HDM

We present a comprehensive analysis of observing a light Higgs boson in the mass range $70$ -- $110$ GeV at the 13/14 TeV LHC, in the context of the type-I two-Higgs-doublet model. The decay of the light Higgs to a pair of bottom quarks is dominant in most parts of the parameter space, except in the fermiophobic limit. Here its decay to bosons, (mainly a pair of photons), becomes important. We perform an extensive collider analysis for the $b\bar{b}$ and $γγ$ final states. The light scalar is tagged in the highly boosted regimes for the $b \bar{b}$ mode to reduce the enormous QCD background. This decay can be observed with a few thousand fb$^{-1}$ of integrated luminosity at the LHC. Near the fermiophobic limit, the decay of the light Higgs to a pair of photons can even be probed with a few hundred fb$^{-1}$ of integrated luminosity at the LHC.

hep-ph

Mixed Higgs-Radion States at the LHC -- a Detailed Study

Light radions constitute one of the few surviving possibilities for observable new particle states at the sub-TeV level which arise in models with extra spacetime dimensions. It is already known that the 125 GeV state discovered at CERN is unlikely to be a pure radion state, since its decays resemble those of the Standard Model Higgs boson too closely. However, due to experimental errors in the measured decay widths, the possibility still remains that it could be a mixture of the radion with one (or more) Higgs states. We use the existing LHC data at 8 and 13 TeV to make a thorough investigation of this possibility. Not surprisingly, it turns out that this model is already constrained quite effectively by direct LHC searches for an additional scalar heavier than 125 GeV. We then make a detailed study of the so-called 'conformal point', where this heavy state practically decouples from (most of) the Standard Model fields. Some projections for the future are also included.

hep-ph

Dissecting new physics models through kinematic edges

Kinematic edges in the invariant mass distributions of different final state particles are typically a signal of new physics. In this work we propose a scenario wherein these edges could be utilised in discriminating between different classes of models. To this effect, we consider the resonant production of a heavy Higgs like resonance (H 1 ) as a case study. Such states are a characteristic feature of many new physics scenarios beyond the Standard Model (SM). In the event of a discovery, it is essential to identify the true nature of the underlying theory. In this work we propose a channel, $H_1 \rightarrow t_2 t$, where t_2 is a vector-like gauge singlet top-partner that decays into W b, Zt, ht. Invariant mass distributions constructed out of these final states are characterized by the presence of kinematic edges, which are unique to the topology under consideration. Further, since all the final state particles are SM states, the position in the edges of these invariant mass distributions can be used to exclusively determine the masses of the resonances. Observation of these features are meant to serve as a trigger, thereby mandating a more detailed analysis in a particular direction of parameter space. The absence of these edge like features, in the specific invariant mass distributions considered here, in minimal versions of supersymmetric models (MSSM) also serves as a harbinger of such non MSSM-like scenarios.

hep-ph

Probing Higgs-radion mixing in warped models through complementary searches at the LHC and the ILC

We consider the Higgs-radion mixing in the context of warped space extra dimensional models with custodial symmetry and investigate the prospects of detecting the mixed radion. Custodial symmetries allow the Kaluza-Klein excitations to be lighter, and protect Zbb to be in agreement with experimental constraints. We perform a complementary study of discovery reaches of the Higgs-radion mixed state at the 13 and 14 TeV LHC and at the 500 and 1000 GeV ILC. We carry out a comprehensive analysis of the most significant production and decay modes of the mixed radion in the 80 GeV - 1 TeV mass range, and indicate the parameter space that can be probed at the LHC and the ILC. There exists a region of the parameter space which can be probed, at the LHC, through the diphoton channel even for a relatively low luminosity of 50 fb^{-1}. The reach of the 4-lepton final state, in probing the parameter space is also studied in the context of 14 TeV LHC, for a luminosity of 1000 fb^{-1}. At the ILC, with an integrated luminosity of 500 fb^{-1}, we analyze the Z-radion associated production and the WW fusion production, followed by the radion decay into bb and W+W-. The WW fusion production is favored over the Z-radion associated channel in probing regions of the parameter space beyond the LHC reach. The complementary study at the LHC and the ILC is useful both for the discovery of the radion and the understanding of its mixing sector.

hep-ph

Radion Candidate for the LHC Diphoton Resonance

The recent observation of a modest excess in diphoton final states at the LHC, by both the ATLAS and CMS Collaborations, has sparked off the expected race among theorists to find the right explanation for this proto-resonance, assuming that the signal will survive and not prove to be yet another statistical fluctuation. We carry out a general analysis of this `signal' in the case of a scalar which couples only to pairs of gluons (for production) and photons (for diphoton decay modes), and establish that an explanation of the observed resonance, taken together with the null results of new physics searches in all the other channels, requires a scalar with rather exotic behaviour. We then demonstrate that a fairly simple-minded extension of the minimal Randall-Sundrum model can yield a radion candidate which might reproduce this exotic behaviour.

hep-ph

Probing the light radion through diphotons at the Large Hadron Collider

A radion in a scenario with a warped extra dimension can be lighter than the Higgs boson, even if the Kaluza-Klein excitation modes of the graviton turn out to be in the multi-TeV region. The discovery of such a light radion would be gateway to new physics. We show how the two-photon mode of decay can enable us to probe a radion in the mass range 60 - 110 GeV. We take into account the diphoton background, including fragmentation effects, and include cuts designed to suppress the background to the maximum possible extent. Our conclusion is that, with an integrated luminosity of 3000 $\rm fb^{-1}$ or less, the next run of the Large Hadron Collider should be able to detect a radion in this mass range, with a significance of 5 standard deviations or more.

hep-ph

Searching for an elusive charged Higgs at the Large Hadron Collider

We study the signals for a "fermiophobic" charged Higgs boson present in an extension of the standard model with an additional Higgs doublet and right handed neutrinos, responsible for generating Dirac-type neutrino masses. We study the pair production of the charged Higgs at the Large Hadron Collider (LHC), which can be relatively light and still allowed by experimental data. The charged Higgs decays dominantly into a $W$ boson and a very light neutral scalar present in the model, which decays invisibly and passes undetected. We find that the signal for such a charged Higgs is overwhelmed by the standard model background and will prove elusive at the 8 TeV run of the LHC. We present a cut-flow based analysis to pinpoint a search strategy at the 14 TeV run of the LHC which can achieve a signal significance of 5$σ$ for a given mass range of the charged Higgs.

hep-ph

Reconciling small radion vacuum expectation values with massive gravitons in an Einstein-Gauss-Bonnet warped geometry scenario

In the usual 5-dimensional Randall-Sundrum scenario with warped geometry of the extra compact dimension, the Goldberger-Wise mechanism for stabilisation of the radius of compactification can lead to a scalar field called the radion. The radion can have implications in TeV-scale physics, which can be especially noticeable if its vacuum expectation value (vev) is not far above a TeV. However a large mass of the first graviton excitation, which seems to be suggested by recent search limit, tends to make the radion vev, far too large in the minimal model. We show that this is not the case if a Gauss-Bonnet term, containing higher powers of the curvature, is present in the 5-dimensional action. As a result, a radion with vev in the range 1-1.5 TeV can be consistent with the first graviton excitation mass well above 3 TeV.

hep-ph

An updated analysis of radion-higgs mixing in the light of LHC data

We explore the constraints on the parameter space of a Randall-Sundrum warped geometry scenario, where a radion field arises out of the attempt to stabilise the radius of the extra compact spacelike dimension, using the most recent data from higgs searches at the Large Hadron Collider (LHC) and the Tevatron. We calculate contributions from both the scalar mass eigenstates arising from radion-higgs kinetic mixing in all important search channels. The most important channel to be affected is the decay via WW*, where no invariant mass peak can discern the two distinct physical states. Improving upon the previous studies, we perform a full analysis in the WW* channel, taking into account the effect of various cuts and interference when the two scalar are closely spaced. We examine both cases where the experimentally discovered scalar is either 'higgs-like' or 'radion-like'. The implications of a relatively massive scalar decaying into a pair of 125 GeV scalars is also included. Based on a global analysis of the current data, including not only a single 125 GeV scalar but also another one with mass over the range 110 to 600 GeV, we obtain the up-to-date exclusion contours in the parameter space. Side by side, regions agreeing with the data within 68% and 95% confidence level based on a χ^2-minimisation procedure, are also presented.

hep-ph