arXiv subjects

N. G. Deshpande

Publications and source records attributed to N. G. Deshpande.

At least 19 recordsLinked to original sources

arXiv2026

Implications of the evidence for direct $\mathbf{CP}$ violation in $D\to π^+π^-$ decays

The observation of $CP$ violation in the difference of $CP$ asymmetries between $D\to K^+K^-$ and $D\to π^+π^-$ has raised a debate whether the observed asymmetries can be regarded as a signal of physics beyond the standard model (SM). In this paper we obtain all the topological amplitudes and isospin amplitudes directly from measured observables for $D\to ππ$. These results unambiguously imply a very large penguin contribution, having a central value $4.74$ times the magnitude of the amplitude for $D^0\toπ^+ π^-$. This fitted central value differs from a reasonable SM estimate of $10\%$ with a significance greater than $3.3σ$. In contrast to previous studies, we present model-independent arguments based only on unitarity of re-scattering amplitudes to show that large penguins cannot arise from re-scattering alone and likely indicate physics beyond the SM. In a model-independent approach we show how a very small contribution from physics beyond the SM with a large weak phase alleviates the problem.

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arXiv2023

Extracting $γ$ from CP violating decays of bottom baryons

The observation of CP violation in meson decays is a testament to the Cabibbo-Kobayashi-Maskawa (CKM) quark mixing paradigm, and an integral part of the Standard Model (SM). The SM also predicts the existence of CP violation in baryon decays that is yet to be observed. A critical test of the SM requires that CP violation be measured in baryon decays as well, in order to verify that it agrees with the measurement using meson decays. In this paper, we propose a modification to the recently proposed method to measure CP violating phase $γ$ in $b$-baryons, using interference arising implicitly due to Bose symmetry considerations of the decay amplitudes.

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arXiv2022

Measuring $\mathbf{CP}$ violating phase in beauty baryon decays

One of the outstanding problems in physics is to explain the baryon-anti-baryon asymmetry observed in nature. According to the well-known Sakharov criterion for explaining the observed asymmetry, it is essential that $CP$ violation exist. Even though $CP$ violation has been observed in meson decays and is an integral part of the standard model (SM), measurements in meson decays indicate that $CP$ violation in the SM is insufficient to explain the observed baryon-anti-baryon asymmetry. SM predicts the existence of yet to be observed $CP$ violation in baryon decays. A critical test of the SM requires that $CP$ violation be measured in baryon decays as well, in order to verify that it agrees with the measurement using meson decays. In this letter we propose a new method to measure $CP$ violating phase in $b$-baryons, using interference arising implicitly due to Bose symmetry considerations of the decaying amplitudes.

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arXiv2020

Beauty baryon non-leptonic decays into decuplet baryons and $CP$-asymmetries based on $SU(3)$-Flavor analysis

We consider charmless weak decays of beauty-baryons into decuplet baryons and pseudoscalar mesons in a general framework based on $SU(3)$-flavor decomposition of the decay amplitudes. The dynamical assumption independent $SU(3)$ analysis accounts for the effects of an arbitrarily broken $SU(3)$ symmetry in these decays. An alternative approach in terms of quark diagrams is also provided and compared with the $SU(3)$ decomposition in the limit of exact $SU(3)$-flavor symmetry. Furthermore, the symmetries of the effective Hamiltonian is used to relate or neglect reduced $SU(3)$ amplitudes to derive several sum rule relations between amplitudes and relations between $CP$ asymmetries in these decays and identify those that hold even if $SU(3)$ is broken.

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arXiv2019

Non-leptonic beauty baryon decays and $CP$-asymmetries based on $SU(3)$-Flavor analysis

We consider hadronic weak decays of beauty-baryons into charmless baryons and pseudoscalar mesons in a general framework based on $SU(3)$ decomposition of the decay amplitudes. The advantage of the approach lies in the ability to perform an $SU(3)$ analysis of these decays without any particular set of dynamical assumptions while accounting for the effects of an arbitrarily broken $SU(3)$ flavor symmetry. Dictated by the symmetries of the effective Hamiltonian that allow us to relate or neglect reduced $SU(3)$ amplitudes, we derive several sum rule relations between amplitudes and relations between $CP$ asymmetries in these decays and identify those that hold even if $SU(3)$ is broken.

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arXiv2016

Consequences of R-Parity violating interactions for anomalies in $\bar B\to D^{(*)} τ\bar ν$ and $b\to s μ^+μ^-$

We investigate the possibility of explaining the enhancement in semileptonic decays of $\bar B \to D^{(*)} τ\bar ν$, the anomalies induced by $b\to sμ^+μ^-$ in $\bar B\to (K, K^*, ϕ)μ^+μ^-$ and violation of lepton universality in $R_K = Br(\bar B\to K μ^+μ^-)/Br(\bar B\to K e^+e^-)$ within the framework of R-parity violating (RPV) MSSM. Exchange of down type right-handed squark coupled to quarks and leptons yield interactions which are similar to leptoquark induced interactions that have been proposed to explain the $\bar B \to D^{(*)} τ\bar ν$ by tree level interactions and $b\to s μ^+μ^-$ anomalies by loop induced interactions, simultaneously. However, the Yukawa couplings in such theories have severe constraints from other rare processes in $B$ and $D$ decays. Although this interaction can provide a viable solution to $R(D^{(*)})$ anomaly, we show that with the severe constraint from $\bar B \to K ν\bar ν$, it is impossible to solve the anomalies in $b\to s μ^+μ^-$ process simultaneously.

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arXiv2015

A model independent method for quantitative estimation of $SU(3)$ flavor symmetry breaking using Dalitz plot

The light hadron states are satisfactorily described in the quark model using $SU(3)$ flavor symmetry. If the $SU(3)$ flavor symmetry relating the light hadrons were exact, one would have an exchange symmetry between these hadrons arising out of the exchange of the up, down and strange quarks. This aspect of $SU(3)$ symmetry is used extensively to relate many decay modes of heavy quarks. However, the nature of the effects of $SU(3)$ breaking in such decays is not well understood and hence, a reliable estimate of $SU(3)$ breaking effects is missing. In this work we propose a new method to quantitatively estimate the extent of flavor symmetry breaking and better understand the nature of such breaking using Dalitz plot. We study the three non-commuting $SU(2)$ symmetries (subsumed in $SU(3)$ flavor symmetry): isospin (or $T$-spin), $U$-spin and $V$-spin, using the Dalitz plots of some three-body meson decays. We look at the Dalitz plot distributions of decays in which pairs of the final three particles are related by two distinct $SU(2)$ symmetries. We show that such decay modes have characteristic distributions that enable the measurement of violation of each of the three $SU(2)$ symmetries via Dalitz plot asymmetries in a single decay mode. Experimental estimates of these easily measurable asymmetries would help in better understanding the weak decays of heavy mesons into both two and three light mesons.

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arXiv2014

On testing violations of Bose and $CPT$ symmetries via Dalitz plots and Dalitz `prism'

Bose symmetry and $CPT$ symmetry are two very fundamental symmetries of Nature. However, the validity of these symmetries in diverse phenomena must be verified by experiments. We propose new techniques to probe these two fundamental symmetries in the realm of mesons by using the Dalitz plot of a few three-body meson decays. Since these symmetries are very fundamental in nature, their violations, if any, are expected to be extremely small. Hence observing their violations requires study of a huge data sample. In this context we introduce a new three-dimensional plot which we refer to as the Dalitz 'prism'. This provides an innovative means for acquiring the huge statistics required for such studies. Using the Dalitz plots and the Dalitz prisms we chart out the way to probe the violations of Bose and $CPT$ symmetries in a significant manner. Since mesons are unstable and composite particles, testing the validity of Bose symmetry and the $CPT$ symmetry in these cases are of paramount importance for fundamental physics.

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arXiv2013

A new technique to observe direct CP Violation in D mesons using Bose Symmetry and Dalitz Plot

We present a new and sensitive method to observe direct CP violation in $D$ mesons using Bose symmetry and Dalitz plot. We apply the method to processes such as $B \to D^0\bar{D}^0 P$, where $P$ is either a $K$ or a $π$. By choosing to reconstruct $D$ mesons only through their decays into CP eigenstates, we show that any asymmetry in the Dalitz plot can arise only through direct CP violation. We further show how CP violation parameters can be determined. Since the approach involves only Bose symmetry, the method is applicable to any multi-body process that involves $D^0\bar{D}^0$ in the final state. We briefly discuss how $B\to D^* \bar{D}^* P$ can also be used in a similar way.

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arXiv2013

An analysis of B meson decays to two light pseudoscalar nonets with deltaS=1 in QCD factorization approach

We have performed a numerical analysis of branching ratios and direct CP-asymmetries of B meson decays to two light pseudoscalar nonets with deltaS=1 using QCD improved factorization. The parameters related to B meson including its semileptonic form factors, strange quark mass and the CKM phase angle have been varied over a limited range and phenomenological parameters used to parameterize divergences in hard spectator scattering and weak annihilation have been varied over a wide range simultaneously with an aim to achieve a fit of branching ratios and some direct CP-asymmetries. A good fit for the majority of the parameters has been achieved indicating that the standard model is quite satisfactory in accounting for these processes.

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arXiv2013

Hints of R-parity violation in B decays into $τν$

In this article we show that the recently observed enhanced semi-leptonic and leptonic decay rates of the B meson into τνmodes can be explained within the frame work of R-parity violating (RPV) MSSM. In particular, RPV contributions involving the exchange of right-handed down-type squarks give a universal contribution to the B+ --> τν, B --> D τνand the B --> D* τνdecays. We find that the masses and couplings that explain the enhanced B decay rates are phenomelogically viable and the squarks can possibly be observed at the LHC.

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arXiv2012

Anomalous Triple Gauge Boson Couplings in $e^{-}e^{+} \to γγ$ for Non Commutative Standard Model

We investigate $e^{+}e^{-}\to γγ$ process within the Seiberg-Witten expanded noncommutative standard model(NCSM) scenario in the presence of anomalous triple gauge boson couplings. This study is done with and without initial beam polarization and we restrict ourselves to leading order effects of non commutativity i.e. $O(Θ)$. The non commutative(NC) corrections are sensitive to the electric component($\vecΘ_E$) of NC parameter. We include the effects of earth rotation in our analysis. This study is done by investigating the effects of non commutativity on different time averaged cross section observables. We have also defined forward backward asymmetries which will be exclusively sensitive to anomalous couplings. We have looked into the sensitivity of these couplings at future experiments at the International Linear Collider(ILC). This analysis is done under realistic ILC conditions with the Center of mass energy(c.m.) $\sqrt{s}=800$GeV and integrated luminosity L=500fb${}^{-1}$. The scale of non commutativity is assumed to be $Λ= 1$TeV. The limits on anomalous couplings of the order $10^{-1}$ from forward backward asymmetries while much stringent limits of the order $10^{-2}$ from total cross section are obtained if no signal beyond SM is seen.

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arXiv2011

Determination of Weak Amplitudes using Bose Symmetry and Dalitz Plots

We present a new method using Dalitz plot and Bose symmetry of pions that allows the complete determination of the magnitudes and phases of weak decay amplitudes. We apply the method to process like B->K^* pi, with the subsequent decay of K^* -> K pi. Our approach enables the additional measurement of an isospin amplitude without any theoretical assumption. This advance will help in measuring weak phase and probing for new physics beyond standard model with fewer assumptions.

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arXiv2011

TeV Scale Implications of Non Commutative Space time in Laboratory Frame with Polarized Beams

We analyze $e^{+}e^{-}\rightarrow γγ$, $e^{-}γ\rightarrow e^{-}γ$ and $γγ\rightarrow e^{+}e^{-} $ processes within the Seiberg-Witten expanded noncommutative scenario using polarized beams. With unpolarized beams the leading order effects of non commutativity starts from second order in non commutative(NC) parameter i.e. $O(Θ^2)$, while with polarized beams these corrections appear at first order ($O(Θ)$) in cross section. The corrections in Compton case can probe the magnetic component($\vecΘ_B$) while in Pair production and Pair annihilation probe the electric component($\vecΘ_E$) of NC parameter. We include the effects of earth rotation in our analysis. This study is done by investigating the effects of non commutativity on different time averaged cross section observables. The results which also depends on the position of the collider, can provide clear and distinct signatures of the model testable at the International Linear Collider(ILC).

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arXiv2011

$μ- e$ Conversion With Four Generations

We study $μ- e$ conversion with sequential four generations. A large mass for the fourth generation neutrino can enhance the conversion rate by orders of magnitude. We compare constraints obtained from $μ- e$ conversion using experimental bounds on various nuclei with those from $μ\to e γ$ and $μ\to e\bar e e$. We find that the current bound from $μ- e$ conversion with Au puts the most stringent constraint in this model. The relevant flavor changing parameter $λ_{μe} = V^*_{μ4}V_{e4}^{}$ is constrained to be less than $1.6\times 10^{-5}$ for the fourth generation neutrino mass larger than 100 GeV. Implications for future $μ-e$ conversion, $μ\to eγ$ and $μ\to e\bar e e$ experiments are discussed.

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arXiv2010

D0 Dimuon Asymmetry in $B_s - \bar B_s$ Mixing and Constraints on New Physics

We study the consequences of the large dimuon asymmetry observed at D0. Physics beyond the standard model (SM) in $B_s-\bar B_s$ mixing is required to explain the data. We first present a detailed analysis for model independent constraints on physics beyond the SM, and then study the implications for theoretical models which modify the SM results in different ways, such as $Z'$ with FCNC and R-parity violating SUSY contributions.

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arXiv2010

The Family SU(2)_l x SU(2)_h x U(1) Model

We consider extension of the standard model $SU(2)_l \times SU(2)_h \times U(1)$ where the first two families of quarks and leptons transform according to the $SU(2)_l$ group and the third family according to the $SU(2)_h$ group. In this approach, the largeness of top-quark mass is associated with the large vacuum expectation value of the corresponding Higgs field. The model predicts almost degenerate heavy $W'$ and $Z'$ bosons with non-universal couplings, and extra Higgs bosons. We present in detail the symmetry breaking mechanism, and carry out the subsequent phenomenology of the gauge sector. We compare the model with electroweak precision data, and conclude that the extra gauge bosons and the Higgs bosons whose masses lie in the TeV range, can be discovered at the LHC.

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arXiv2008

Invisible Higgs boson, continuous mass fields and unHiggs mechanism

We explore the consequences of an electroweak symmetry breaking sector which exhibits approximately scale invariant dynamics -- i.e., nontrivial fixed point behavior, as in unparticle models. One can think of an unHiggs as a composite Higgs boson with a continuous mass distribution. We find it convenient to represent the unHiggs in terms of a Kallen-Lehmann spectral function, from which it is simple to verify the generation of gauge boson and fermion masses, and unitarization of WW scattering. We show that a spectral function with broad support, which corresponds to approximate fixed point behavior over an extended range of energy, can lead to an effectively invisible Higgs particle, whose decays at LEP or LHC could be obscured by background.

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