arXiv subjects

N. G. Deshpande

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

At least 37 records · Page 2Linked to original sources

arXiv2008

Unparticle Realization Through Continuous Mass Scale Invariant Theories

We consider scale invariant theories of continuous mass fields, and show how interactions of these fields with the standard model can reproduce unparticle interactions. There is no fixed point or dimensional transmutation involved in this approach. We generalize interactions of the standard model to multiple unparticles in this formalism and explicitly work out some examples, in particular we show that the product of two scalar unparticles behaves as a normalized scalar unparticle with dimension equal to the sum of the two composite unparticle dimensions. Extending the formalism to scale invariant interactions of continuous mass fields, we calculate three point function of unparticles.

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arXiv2008

Möller and Bhabha scattering in the noncommutative standard model

We study the Möller and Bhabha scattering in the noncommutative extension of the standard model(SM) using the Seiberg-Witten maps of this to first order of the noncommutative parameter $θ_{μν}$. We look at the angular distribution $dσ/dΩ$ to explore the noncommutativity of space-time at around $Λ_{NC} \sim$ TeV and find that the distribution deviates significantly from the one obtained from the commutative version of the standard model.

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arXiv2007

Accurate measurement of the D0-D0bar mixing parameters

We propose a new method to determine the mass and width differences of the two D meson mass-eigenstates as well as the CP violating parameters associated with D^0-\bar{D}^0 mixing. We show that an accurate measurement of all the mixing parameters is possible for an arbitrary CP violating phase, by combining observables from a time dependent study of D decays to a doubly Cabibbo suppressed mode with information from a CP eigenstate. As an example we consider D^0-> K^{*0} π^0 decays where the K^{*0} is reconstructed in both K^+π^- and K_Sπ^0. We also show that decays to the CP eigenstate D-> K^+K^- together with D-> K^+π^- can be used to extract all the mixing parameters. A combined analysis using D^0-> K^{*0} π^0 and D-> K^+K^- can also be used to reduce the ambiguity in the determination of parameters.

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arXiv2007

Long range forces and limits on unparticle interactions

Couplings between standard model particles and unparticles from a nontrivial scale invariant sector can lead to long range forces. If the forces couple to quantities such as baryon or lepton (electron) number, stringent limits result from tests of the gravitational inverse square law. These limits are much stronger than from collider phenomenology and astrophysics.

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arXiv2007

Supersymmetric Unparticle Effects on Higgs Boson Mass and Dark Matter

We propose a model that introduces a supersymmetric unparticle operator in the minimal supersymmetric Standard Model. We analyze the lowest dimension operator involving an unparticle. This operator behaves as a Standard Model gauge singlet and it introduces a new parameter into the Higgs potential which can provide an alternative way to relax the upper limit on the lightest Higgs boson mass. This operator also introduces several unparticle interactions which can induce a neutral Higgsino to decay into a spinor unparticle. It also induces violation of scale invariance around the electroweak scale. It is necessary for the scale of this violation to be larger than the lightest supersymmetric particle mass to maintain the latter as the usual weakly interacting massive particle dark matter candidate. An alternative is to have unparticle state as dark matter candidate. We also comment on some collider implications.

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arXiv2007

Spontaneous CP Violating Phase as The CKM Matrix Phase

We propose that the CP violating phase in the CKM mixing matrix is identical to the CP phases responsible for the spontaneous CP violation in the Higgs potential. A specific multi-Higgs model with Peccei-Quinn (PQ) symmetry is constructed to realize this idea. The CP violating phase does not vanish when all Higgs masses become large. There are flavor changing neutral current (FCNC) interactions mediated by neutral Higgs bosons at the tree level. However, unlike general multi-Higgs models, the FCNC Yukawa couplings are fixed in terms of the quark masses and CKM mixing angles. Implications for meson-anti-meson mixing, including recent data on $D-\bar D$ mixing, and neutron electric dipole moment (EDM) are studied. We find that the neutral Higgs boson masses can be at the order of one hundred GeV. The neutron EDM can be close to the present experimental upper bound.

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arXiv2007

Implications of Canonical Gauge Coupling Unification in High-Scale Supersymmetry Breaking

We systematically construct two kinds of models with canonical gauge coupling unification and universal high-scale supersymmetry breaking. In the first we introduce standard vector-like particles while in the second we also include non-standard vector-like particles. We require that the gauge coupling unification scale is from 5 x 10^{15} GeV to the Planck scale, that the universal supersymmetry breaking scale is from 10 TeV to the unification scale, and that the masses of the vector-like particles (M_V) are universal and in the range from 200 GeV to 1 TeV. Using two-loop renormalization group equation (RGE) running for the gauge couplings and one-loop RGE running for Yukawa couplings and the Higgs quartic coupling, we calculate the supersymmetry breaking scales, the gauge coupling unification scales, and the corresponding Higgs mass ranges. When the vector-like particle masses are less than 1 TeV, these models can be tested at the LHC.

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arXiv2006

Flavor Changing Effects in Family Nonuniversal Z' Models

Flavor-changing and CP-violating interactions of Z' to fermions are generally present in models with extra U(1) gauge symmetry that are string-inspired or related to broken gauged family symmetry. We study the consequences of such couplings in fermion electric dipole moments, muon g-2, and K and B meson mixings. From experimental limits or measured values, we constrain the off-diagonal Z' couplings to fermions. Some of these constraints are comparable or stronger than the existing constraints obtained from other observables.

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arXiv2006

Constraints on flavor-changing Z' models by B_s mixing, Z' production, and B_s -> μ^+ μ^-

Certain string-inspired Z' models have non-universal interactions to three families of fermions and induced tree-level flavor-changing couplings. We use recent results on B_s-anti-B_s mixing to constrain the size of the flavor-changing couplings in the b-s sector. In some highly predictive Z' models, such a constraint on b-s coupling can be translated into the flavor-diagonal couplings. Based on the Z' production limits at the Tevatron, we obtain the limit on the leptonic couplings of Z' and then make predictions for B_s -> μ^+ μ^- branching ratios. We conclude that with the present constraints from B_s mixing and Z' production, the muonic decay of $B_s$ may not be observed at the Tevatron if the projected integrated luminosity is less than O(5-10) fb.

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arXiv2005

On the Possibility of a New Boson X^0 (214 MeV) in Sigma^+ -> p mu^+ mu^-

We consider the existence of the state X^0 (214 MeV) in Sigma^+ -> p mu^+ mu^- decay found by the HyperCP collaboration. We assume that a fundamental spin zero boson X^0 coupled to quarks leads to flavor changing s -> d X^0 process. We estimate the scalar and pseudoscalar coupling constants by considering Sigma^+ -> p X^0 and K^+ -> pi^+ X^0 processes, and find that pseudoscalar coupling dominates. We then evaluate the branching ratios for K_L -> pi^0 pi^0 X^0, pi^+ pi^- X^0 and Omega^- -> Xi^- X^0 decays. All these rates are found to be in the measurable ranges. We also comment on X^0 coupling to muons and constraints from muon g-2.

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arXiv2005

Signals for CP Violation in Split Supersymmetry

Split supersymmetry is characterized by relatively light chargino and neutralino sector and very heavy sfermion sector. We study the consequence of CP violation in this scenario by evaluating two-loop contributions to electric dipole moments of fermions from Higgs-photon as well as $W$-$W$ diagrams. These contributions add coherently and produce electron and neutron electric dipole moments close to present bounds. We then explore Higgs production at a photon-photon collider, and consider the feasibility of measuring CP violating $hγγ$ coupling induced by chargino loops. Methods of enhancing the sensitivity are discussed. For lower chargino masses and lower Higgs boson masses, the effect of the CP violation can be observed with 90% confidence level significance.

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arXiv2004

New Source of CP violation in B physics ?

In this talk we discuss how the down type left-right squark mixing in Supersymmetry can induce a new source of CP violation in the time dependent asymmtries in B --> phi K process. We use QCD improved factorization process to calculate the hadronic matrix element for the process and find the allowed parameter space for $ρ$ and $ϕ$, the magnitude and phase of the down type LR(RL) squark mixing parameter $δ^{bs}_{LR(RL)}$. In the same allowed regin we calculate the expected CP asymmtries in the $B \to ϕK^{*}$ process.

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arXiv2004

Constraints on New Physics from $K \to πν\barν$

We study constraints on new physics from the recent measurement of Br ($K^+ \to π^+ ν\bar ν)$ by the E787 and E949 Collaborations. In our analysis we consider two models of new physics: $(a)$ extra down type singlet quark model (EDSQ) and $(b)$ R-parity violating Minimal Supersymmetric Standard Model(MSSM). We find that $K^+\to π^+ ν\bar ν$ along with other processes like $K_L \to μ^+ μ^-, ε^\prime/ε$ provide useful bounds on the parameter $U_{sd}$, characterizing the off-diagonal $Z-d-\bar s $ coupling of model $(a)$. The bounds on the ${\rm Re}(U_{sd})$ from $(K_L \to μ^+μ^-)_{\rm SD}$ and ${\rm Im}(U_{sd})$ from $ε^\prime/ε$ are so tight that the branching ratio of $K^+\to π^+ ν\bar ν$ can exceed the standard model value by at most a factor of two For model b), we also obtain stringent bounds on certain combinations of product of two $\lp_{ijk}$ couplings originating from $L$ number violating operator $ L_i Q_j D^c_k $ using $K^+ \to π^+ ν\bar ν$ and $K_L \to μ^+ μ^-$ processes. Even with the stringent constraints on $U_{sd}$ (in model $(a)$) and on products of two $\rp$couplings (model $(b)$), we find that the branching ratios for $K_L \to π^0 ν\bar ν$ and $K_L \to π^0 e^+ e^-$ can be substantially different in both the above models from those predicted in the standard model.

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arXiv2004

Flavor and CP violating Z exchange and the rate asymmetry in B --> phi K_S

Recent measurements of time dependent CP asymmetry in B --> phi K_S, if confirmed, would indicate a new source of CP violation. We examine flavor violating tree-level Z currents in models with extra down-type quark singlets that arise naturally in string compactified gauge groups like E_6. We evaluate the new operators at the scale mu = m_b in NLO, and using QCD improved factorization to describe B --> phi K_S, find the allowed range of parameters for rho and psi, the magnitude and phase of the flavor violating parameter U_{bs}. This allowed range does satisfy the constraint from flavor changing process b --> s l+ l- . However, further improvement in measurement of these rates could severely constrain the model.

hep-ph↗

arXiv2004

CP violating SUSY effects in Penguin dominated modes B -> PHI K and B -> PHI K*

Recent measurement of time dependent asymmetries in $B \to ϕK$ are indicative of a new source of CP violation. We examine squark mixing in SUSY as this new source, and using QCD improved factorization method to describe $B \to ϕK $ decay, find the allowed range of parameter space for $ρ$ and $ψ$, the magnitude and phase of the down type LR(RL) squark mixing parameter $δ^{bs}_{LR(RL)}$. We then study $B \to ϕK^{*}$ and calculate the expected CP asymmetries in the same range of parameter space. We find that this asymmetry is in the range 15% to $20% $ for acceptable value of $B \to phi K^{*}$ branching ratio. We also predict the helicity dependent CP asymmetries in the same parameter space.

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arXiv2003

Higgs production in association with top quark pair at e+e- colliders in theories of higher dimensional gravity

The models of large extra compact dimensions, as suggested by Arkani-Hamed, Dimopoulos and Dvali, predict exciting phenomenological consequences with gravitational interactions becoming strong at the TeV scale. Such theories can be tested at the existing and future colliders. In this paper, we study the contribution of virtual Kaluza-Klein excitations in the process $e^+e^- \to t \bar t H $ at future linear collider (NLC). We find that the virtual exchange KK gravitons can modify the cross-section $σ(e^+e^- \to t \bar t H)$ significantly from its Standard Model value and will allow the effective string scale to be probed up to 7.9 TeV.

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arXiv2003

Invisible decays of Higgs and other mesons in models with singlet neutrinos in large extra dimensions

In light of current atmospheric neutrino oscillation data, we revisit the invisible decay of the standard model Higgs boson and other pseudoscalar mesons which can be enhanced because of large number of KK modes in models with right handed singlet neutrinos in large extra dimensions. We find that the invisible decay rate of Higgs can be as large as $H\to b \bar b $ decay rate only for a very restricted region of parameter space. This parameter space is even further restricted if one demands that the dimensionless neutrino Yukawa coupling $ł$ is O(1). We have also studied the scenarios where singlet neutrino propagate in a sub-space, which lowers the string scale $M_{\ast}$ and keeps neutrino Yukawa coupling O(1). We have also considered decays of other spin-0 mesons to $ν\barν$ and found the rates to be too small for measurement.

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arXiv2003

The Z -> gamma gamma, gg Decays in the Noncommutative Standard Model

On noncommutative spacetime, the Standard Model allows new, usually Standard Model forbidden, triple gauge boson interactions. In this letter we propose the Standard Model strictly forbidden Z -> gamma gamma and Z -> gg decay modes coming from the gauge sector of the Noncommutative Standard Model as a place where noncommutativity could be experimentally discovered.

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