arXiv subjects

Soumya Sadhukhan

Publications and source records attributed to Soumya Sadhukhan.

25 records · Page 2Linked to original sources

arXiv2016

Status and Prospects of the Two-Higgs-Doublet SU(6)/Sp(6) little-Higgs Model and the Alignment Limit

We study in detail the little-Higgs model proposed by Low, Skiba and Smith with an SU(6)/Sp(6) group structure. The effective theory at the TeV scale is a two-Higgs doublet model (2HDM) with additional heavy vector-like fermions and vector-bosons. We identify a set of independent input parameters and develop expressions for masses and couplings in terms of these. We perform a random scan of the parameter space and find points that satisfy constraints, including the recent 8 TeV LHC Higgs measurements, namely, the Higgs mass, Higgs couplings to the top, bottom, $τ$, $W^\pm$ and $Z$, top-quark mass, and collider bounds on colored vector-like fermions ($t'$ and $b'$), and also precision electroweak constraints. The LHC constraints on the $hWW$ and $hZZ$ couplings are satisfied by being close to the "alignment limit". We find how fine-tuned the model is after including these constraints. For the points that satisfy the constraints, we present the 1-loop effective couplings of the CP-even and CP-odd neutral scalars to two gluons including contributions of standard model and heavy vector-like quarks. We also present the branching ratios of the heavy neutral scalars into the $γγ,\, τ\barτ,\, b\bar b,\, t\bar t, WW, ZZ, Zh, hh$ modes, and the heavy charged scalar into $tb,\, τν, cs, W h$ modes. These will aid searches of the heavy scalars at the LHC and other future colliders.

hep-ph↗

arXiv2016

Constraining wrong-sign $hbb$ couplings with $h \rightarrow Υγ$

The rare decay $h \rightarrow Υγ$ has a very small rate in the Standard Model, due to a strong cancellation between the direct and indirect diagrams. Models with a changed $hbb$ coupling can thus lead to a great increase in this decay. Current limits on two Higgs doublet models still allow for the possibility that the $hbb$ coupling might have a sign opposite to the Standard Model; the so-called "wrong-sign". We show how $h \rightarrow Υγ$ can be used to put limits on the wrong-sign solutions.

hep-ph↗

arXiv2016

750 GeV Diphoton excess from Gauged $B-L$ Symmetry

We show that the recently observed 750 GeV diphoton excess at LHC can be due to the decay of a $SU(2)_L$ singlet scalar particle having 3 units of charge under gauged $B - L$ symmetry. Such a particle arises as an essential ingredient of recently studied gauged $B -L$ extension of the Standard Model with unconventional charge assignment for right handed neutrinos. Apart from being one of the simplest extensions of the Standard Model, the model also contains a dark matter candidate and Dirac neutrinos with naturally small masses.

hep-ph↗

arXiv2016

From Extended theories of Gravity to Dark Matter

In this work, we propose different models of extended theories of gravity, which are minimally coupled to the SM fields, to explain the possibility of a dark matter (DM) candidate, without ad-hoc additions to the Standard Model (SM). We modify the gravity sector by allowing quantum corrections motivated from local $f(R)$ gravity, and non-minimally coupled gravity with SM sector and dilaton field. Using an effective field theory (EFT) framework, we constrain the scale of the EFT and DM mass. We consider two cases-Light DM (LDM) and Heavy DM (HDM), and deduce upper bounds on the DM annihilation cross section to SM particles.

hep-th↗

arXiv2016

Extra Neutral Scalars with Vector-like Fermions at the LHC

Many theories beyond the standard model (BSM) contain new CP-odd and CP-even neutral scalars $ϕ= \{A,H\}$, and new vector-like fermions ($ψ_{VL}$). The couplings of the CP-odd scalar $A$ to two standard model (SM) gauge bosons cannot occur from renormalizable operators in a CP-conserving sector, but can be induced at the quantum loop level. We compute these effective couplings at the 1-loop level induced by the SM fermions and vector-like fermions, present analytical expressions for them, and plot them numerically. Using the 8~TeV Large Hadron Collider (LHC) $γγ$, $τ^{+} τ^{-}$ and $t \bar t$ channel data, we derive constraints on the effective couplings of the $ϕ$ to standard model gauge bosons and fermions. We present the gluon-fusion channel cross-sections of the $ϕ$ at the 8~and~14~TeV LHC, and its branching-ratios into SM fermion and gauge-boson pairs. We present our results first model-independently, and then also for some simple models containing $ϕ$ and $ψ_{VL}$ in the singlet and doublet representations of $SU(2)$. In the doublet case, we focus on the two-Higgs-doublet (2HDM) Type-II and Type-X models in the alignment limit.

hep-ph↗

arXiv2013

Warped Extra Dimensional Benchmarks for Snowmass 2013

The framework of a warped extra dimension with the Standard Model (SM) fields propagating in it is a very well-motivated extension of the SM since it can address both the Planck-weak and flavor hierarchy problems of the SM. We consider signals at the 14 and 33 TeV large hadron collider (LHC) resulting from the direct production of the new particles in this framework, i.e.,Kaluza-Klein (KK) excitations of the SM particles. We focus on spin-1 (gauge boson) and spin-2 (graviton) KK particles and their decays to top/bottom quarks (flavor-conserving) and W/Z and Higgs bosons, in particular. We propose two benchmarks for this purpose, with the right-handed (RH) or LH top quark, respectively, being localized very close to the TeV end of the extra dimension. We present some new results at the 14 TeV (with 300 fb$^-1$ and 3000 fb$^-1$) and 33 TeV LHC. We find that the prospects for discovery of these particles are quite promising, especially at the high-luminosity upgrade.

hep-ph↗

arXiv2013

Collider constraints on Gauss-Bonnet coupling in warped geometry model

In this paper the requirement of a warp solution in an Einstein-Gauss-Bonnet 5D warped geometry is shown to fix the signature of Gauss-Bonnet coupling ($α_{5}$). Further, imposing the phenomenological constraints, obtained from the recently observed Higgs like scalar mass as well as $μ$ parameter of the decay channels ${H}_{0}\rightarrowγγ,τ{\bar τ}$ explored in ATLAS and CMS detectors, we obtain a stringent bound on $α_{5}$ within $(4.8 - 5.1)\times 10^{-7}$.

hep-ph↗