arXiv subjects

S. Rai Choudhury

Publications and source records attributed to S. Rai Choudhury.

At least 19 recordsLinked to original sources

arXiv2019

Direct calculation of time varying Aharonov Bohm effect

The Aharonov-Bohm effect (ABE) for steady magnetic fields is a well known phenomenon. However, if the current in the infinite solenoid that creates the magnetic field is time-dependent, that is in the presence of both magnetic and electric fields, there is no agreement whether the effect would be present. In this note, we try to investigate time varying ABE by a direct calculation in a set-up with a weak time dependent magnetic field. We find that the electric field arising out of the time-varying magnetic field in the path of the electrons does not enter the action integral but only changes the path of the electron from the source to the slits and then on to the detector. We find a frequency dependent AB phase shift. At low frequencies the result smoothly approaches the one for a constant field as the frequency tends towards zero. On the other hand, for high frequencies such that the AB-phase induced in the path of the wave packet oscillates rapidly, the net effect will be very small which is borne out by our results.

quant-ph↗

arXiv2010

Analysis of the ${\bar B} \to {\bar K}_2(1430) \ell^+ \ell^-$ decay

We present an analysis of the decay process ${\bar B} \to {\bar K}_2(1430) \ell^+ \ell^-$, where this process has all the features of the related and well investigated process ${\bar B} \to {\bar K}^*(890) \ell^+ \ell^-$, with theoretically comparable branching ratios. The differential decay rate as well as the forward-backward asymmetry are worked out, where the sensitivity of these to possible right-handed couplings for the related $b \to s$ radiative decay are also investigated.

hep-ph↗

arXiv2009

T-parity odd heavy leptons at LHC

Little Higgs models with T-parity can easily satisfy electroweak precision tests and at the same time give a stable particle which is a candidate for cold dark matter. In addition to little Higgs heavy gauge bosons, this type of models predicts a set of new T-odd fermions, which may show quite interesting signatures at colliders. We study purely leptonic signatures of T-odd leptons at the Large Hadron Collider (LHC).

hep-ph↗

arXiv2009

How delicate are the $f(R)$ gravity models with disappearing cosmological constant?

We consider stability of spherically symmetric solutions in $f(R)$ gravity model proposed by Starobinsky. We find that the model suffers from a severe fine tuning problem when applied to compact objects like neutron stars. The problem can be remedied by introducing a cut off on the mass of the scalar degree of freedom present in the model. A new mass scale associated with neutron stars density is then required for the stabilities of $f(R)$ gravity solutions inside relativistic stars.

gr-qc↗

arXiv2009

Dileptonic signatures of T-odd quarks at the LHC

Little Higgs models are often endowed with a T-parity in order to satisfy electroweak precision tests and give at the same time a stable particle which is a candidate for cold dark matter. This type of models predicts a set of new T-odd fermions in addition to the heavy gauge bosons of the Little Higgs models, which may show interesting signatures at colliders. In this paper, we study the signatures of strong and electroweak pair production of the first two generations of T-odd quarks at the LHC. We focus on the dileptonic signatures (p p to l l j j MET) with (a) opposite-sign dileptons and (b) same-sign dileptons.

hep-ph↗

arXiv2007

$B \to K_1(1270) (\to ρK) \ell^+ \ell^-$ in LEET

Flavour Changing Neutral Current decays of the $B$-meson are a very useful tool for studying possible physics scenarios beyond the Standard Model (SM), where of the many FCNC modes radiative, purely leptonic and semi-leptonic decays of the $B$-meson are relatively clean tests. Within this context the BELLE collaboration has searched for the $B \to K_1(1270) γ$ process and provided an upper bound on this decay. In this work we have used this upper bound in studying the angular coorelations for the related semi-leptonic decay mode $B \to K_1(1270) (\to ρK) \ell^+ \ell^-$, where we have used the form factors that have already been estimated for the $B \to K_1(1270) γ$ mode. Note that the additional form factors that are required were calculated using the Large Energy Effective Theory (LEET).

hep-ph↗

arXiv2006

Lepton flavour violation in The Little Higgs model

Little Higgs models with T-parity have a new source of lepton flavour violation. In this paper we consider the anomalous magnetic moment of the muon \gmtwo and the lepton flavour violating decays \mutoeg and \tautomug in Little Higgs model with T-parity \cite{Goyal:2006vq}. Our results shows that present experimental constraints of \mutoeg is much more useful to constrain the new sources of flavour violation which are present in T-parity models.

hep-ph↗

arXiv2006

Analysis of the $B \to K^*_{2} (\to K π) l^+ l^-$ decay

In this paper we study the angular distribution of the rare B decay $B \to K^*_2 (\to K π) l^+ l^-$, which is expected to be observed soon. We use the standard effective Hamiltonian approach, and use the form factors that have already been estimated for the corresponding radiative decay $B \to K^*_2 γ$. The additional form factors that come into play for the dileptonic channel are estimated using the large energy effective theory (LEET), which enables one to relate the additional form factors to the form factors for the radiative mode. Our results provide, just like in the case of the $K^*(892)$ resonance, an opportunity for a straightforward comparison of the basic theory with experimental results which may be expected in the near future for this channel.

hep-ph↗

arXiv2006

Little Higgs model effects in $γγ\to γγ$

Though the predictions of the Standard Model (SM) are in excellent agreement with experiments there are still several theoretical problems associated with the Higgs sector of the SM, where it is widely believed that some ``{\it new physics}'' will take over at the TeV scale. One beyond the SM theory which resolves these problems is the Little Higgs (LH) model. In this work we have investigated the effects of the LH model on $\gggg$ scattering \cite{Choudhury:2006xa}.

hep-ph↗

arXiv2006

Little Higgs model effects at $γγ$ collider

Though the predictions of the Standard Model (SM) are in excellent agreement with experiments there are still several theoretical problems, such as fine-tuning and the hierarchy problem. These problems are associated with the Higgs sector of the SM, where it is widely believed that some {\it ``new physics"} will take over at the TeV scale. One beyond the SM theory which resolves these problems is the Little Higgs (LH) model. In this work we shall investigate the effects of the LH model on $\gggg$ scattering; where the process $\gggg$ at high energies occurs in the SM through diagrams involving $W$, charged quark and lepton loops (and is, therefore, particularly sensitive to any new physics

hep-ph↗

arXiv2006

Lepton number violation via intermediate black hole processes

Black holes at the TeV scale are investigated in the extra large dimension scenario. We interpret the lightest black hole excitation as a singlet scalar field, and show how interaction terms can be appended to the standard model at the dimension five non-renormalizable level. Lepton family number violation is natural in this model. Muon magnetic moment, and neutrino masses are investigated. We also present a quantization scheme in n dimensions.

hep-ph↗

arXiv2005

Lepton number violation in Little Higgs model

In this note we examine the constraints imposed by muon anomalous magnetic moment ($(g-2)_μ$) and $μ^- \to e^+ e^- e^-$ on lepton number violating (LNV) couplings of the triplet Higgs in Little Higgs (LH) model.

hep-ph↗

arXiv2005

CP violation in the $B \to K \ell^+ \ell^-$ decay

Standard Model (SM) CP asymmetries in $B \to K \ell^+ \ell^-$ are expected to be very small. This feature could help in the understanding of new physics scenarios which predict the existence of CP odd phases in various Wilson coefficients. In this paper we have analyzed the $B \to K \ell^+ \ell^-$ decay in beyond the SM scenarios where the Wilson coefficients have new CP odd phases. The sensitivity of the CP asymmetries on these new weak phases is discussed.

hep-ph↗

arXiv2005

Signatures of new Physics in dileptonic B-decays

Leptonic decays of $B$-mesons are theoretically very clean probes for testing the Standard Model (SM) and possible physics beyond it. Amongst the various leptonic decays of the $B$-meson, the pure dileptonic decay $B \to \ell^+ \ell^-$ is very important as this mode is helicity suppressed in the SM but can be substantially enhanced in some of the models beyond the SM, such as supersymmetric (SUSY) theories and the two Higgs doublet model (2HDM). Although the purely dileptonic decay mode is helicity suppressed in the SM its associated mode $B \to \ell^+ \ell^- γ$ does not have the same suppression, due to the presence of the $γ$ in the final state. In this paper we will also analyse the effects of enhanced $Z$-penguins on these two decay modes.

hep-ph↗

arXiv2005

$K_L \to π^0 ν\barν$ in Little Higgs model

Little Higgs models provides us a new solution of the {\it hierarchy problem} of the SM. The problem is associated with the large difference in scales of SM and plank scale. One of the main features of these models is the existence of a vector like top quark. The CP violating $K_L \to π^0 ν\barν$ process n the SM model is dominated by top quark penguin & box graphs. We examine this process in the Little Higgs model where the top quark sector has significant differences from the Standard Model.

hep-ph↗

arXiv2005

$B_d - \bar{B}_d$ mass difference in Little Higgs model

An alternate solution of hierarchy problem in the Standard Model namely, the Little Higgs model, has been proposed lately. In this work $B_d^0-\bar{B_d^0}$ mass difference in the framework of the Little Higgs model is evaluated. The experimental limits on the mass difference is shown to provide meaningful constraints on the parameter space of the model.

hep-ph↗

arXiv2004

The effects of enhanced Z penguins on lepton polarizations in $B \to X_s \ell^+ \ell^-$

The sensitivity of the $B \to πK$ mode to electroweak penguins and the recent experimental data for the $B \to ππ$, $πK$ modes has given rise to what is known as the ``$B \to πK$ puzzle''. Recently it has been observed that this {\sl puzzle} can be resolved by considering the new physics which can enter via $Z^0$ penguins. In this note we analyze the effect of this enhanced $Z^0$ penguins on the lepton polarization asymmetries of $b \to s \ell^+ \ell^-$.

hep-ph↗

arXiv2003

Lepton polarization correlations in $B \to K^* τ^- τ^+$

In this work we will study the polarizations of both leptons ($τ$) in the decay channel $B\to K^* τ^- τ^+$. In the case of the dileptonic inclusive decay $B\to K^* \ell^- \ell^+$, where apart from the polarization asymmetries of single lepton $\ell$, one can also observe the polarization asymmetries of both leptons simultaneously. If this sort of measurement is possible then we can have, apart from decay rate, FB asymmetry and the six single lepton polarization asymmetries (three each for $\ell^-$ and $\ell^+$), nine more double polarization asymmetries. This will give us a very useful tool in more strict testing of SM and the physics beyond. We discuss the double polarization asymmetries of $τ$ leptons in the decay mode $B\to K^* τ^- τ^+$ within the SM and the Minimal Supersymmetric extensions of it.

hep-ph↗