New Physics in \({\mit \Gamma }_{12}^s: (\bar s b) (\bar \tau \tau )\) Operators

Acta Phys. Pol. B **44**, 127 (2013)

page 127 •

abstract

Measurements performed at the Tevatron of both the like-sign dimuon charge asymmetry in \(B_{d,s}\)-meson samples and the mixing-induced CP asymmetry in \(B_s \to J/\psi \phi \) depart from their Standard Model (SM) predictions. This could be an indication for new CP phases in \(\Delta B = 2\) transitions, preferentially in \(B_s\)–\(\bar B_s\) mixing. The experimental situation, however, remained inconclusive, as it favored values of the element \({\mit \Gamma }_{12}^s\) of the decay matrix in the \(B_s\)-meson system that are notably different from the SM expectation, suggesting the presence of new physics in the \(\Delta B = 1\) sector as well. The very recent LHCb measurements of \(B_s \to J/\psi \phi \) and \(B_s \to J/\psi f_0\), which do not find any evidence for a new-physics phase in the element \(M_{12}^s\) of the mass matrix, point into this direction as well. In this article, we explore the potential size of non-standard effects in \({\mit \Gamma }_{12}^s\) stemming from dimension-six operators with flavor content \((\bar s b) (\bar \tau \tau )\). We show that since the existing constraints imposed by tree- and loop-level mediated \(B_{d,s}\)-meson decays are quite loose, the presence of absorptive new physics of this type would lead to an improved global fit to the current data. The allowed effects are, however, far too small to provide a full explanation of the observed anomalies. Our model-independent conclusions are finally contrasted with explicit analyses of the new-physics effects in \(B_s\)–\(\bar B_s\) mixing that can arise from leptoquarks or \(Z^\prime \) bosons.

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https://www.actaphys.uj.edu.pl/R/44/2/127/pdf

link to the articles list

https://www.actaphys.uj.edu.pl/R/44/2/127

On the Weak Coupling Limit for Massive Yang–Mills

Acta Phys. Pol. B **44**, 177 (2013)

page 177 •

abstract

For small values of the gauge coupling constant, we compare the densities of the energy of the vacuum and of the order parameter, evaluated in the lattice Monte Carlo simulation and in the perturbative field theory at two loop (Minkowski). The continuum calculation allows a very good fit of the simulation results, away from the phase transition line. This confirms the conjecture that the lattice provides a regularization of the (nonrenormalizable) massive Yang–Mills and moreover, it shows the physical meaning of the parameters used in the simulation.

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https://www.actaphys.uj.edu.pl/R/44/2/177/pdf

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https://www.actaphys.uj.edu.pl/R/44/2/177

A Search for Pair Production of the LSP \(\tilde {\nu _{\tau }}\) at the CLIC via RPV Decays

Acta Phys. Pol. B **44**, 195 (2013)

page 195 •

abstract

The pair production of tau sneutrinos at the Compact Linear Collider (CLIC) has been investigated. We assume that tau sneutrino is the lightest supersymmetric particle and decays into \(e\mu \) pair via R-parity violating interactions. Backgroundless subprocess \(e{}^{-}e^{+}\rightarrow \tilde {\nu _{\tau }}\bar {\tilde {\nu _{\tau }}}\rightarrow \mu ^{+}\mu ^{+}e^{-}e^{-} (\mu ^{-}\mu ^{-}e^{+}e^{+})\) is analyzed in details. Achievable limits on Br\(\,(\tilde {\nu }_{\tau }\rightarrow \mu e)\) are obtained depending on \(\tilde {\nu }_{\tau }\) mass. It is shown that CLIC with \(\sqrt {S}=0.5\) TeV and \(L_{\rm int}=2.3\) fb\(^{-1}\) will give opportunity to discover \(\tilde {\nu }_{\tau }\) if its mass is below \(234\) GeV. The CLIC with, \(\sqrt {S}=3\) TeV and \(L_{\rm int}=5.9\) fb\(^{-1}\) will enlarge the discovery region up to \(M_{\tilde {\nu }_{\tau }}=1030\) GeV.

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https://www.actaphys.uj.edu.pl/R/44/2/195/pdf

link to the articles list

https://www.actaphys.uj.edu.pl/R/44/2/195

Associated Production of Different Flavor Heavy Quarks Through \(W'\) Bosons at the LHC

Acta Phys. Pol. B **44**, 203 (2013)

page 203 •

abstract

Associated production of different flavor heavy quarks can provide a probe for \(W'\) bosons at the LHC. We study \(pp\to t'\bar {b'}X\) process with the subsequent decays \(t'\to W^+b\) and \(\bar {b'}\to W^-W^+\bar b\), and compare the results with the \(t\bar {b}\) final state. The effects of the \(W'\) boson to the different flavor pair production cross section are shown to be important in some parameter region for the heavy quark masses of 600 and 700 GeV. We present accessible mass limits for the \(W'\) boson at the LHC with \(\sqrt s=14\) TeV.

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https://www.actaphys.uj.edu.pl/R/44/2/203/pdf

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https://www.actaphys.uj.edu.pl/R/44/2/203

The Surface Gravitational Redshift of the Neutron Star PSR J1614-2230

Acta Phys. Pol. B **44**, 211 (2013)

page 211 •

abstract

Based on the hadronic level, the value range of the surface gravitational redshift of the neutron star PSR J1614-2230 is tried to be determined in the framework of the relativistic mean field theory. It is found that for the neutron star PSR J1614-2230 the ratio of mass \(M\) and radius \(R\) is in the range of \(\sim 0.1692\) to 0.1958 and the surface gravitational redshift is in the range of \(\sim 0.4138\) to 0.5397. However, for a small mass neutron star, which is calculated with the hyperon coupling constant obtained by the constituent quark model [SU(6) symmetry], the ratio of mass \(M\) and radius \(R\) is 0.1221 and the surface gravitational redshift is 0.2507. The surface gravitational redshift of the neutron star PSR J1614-2230 is about one times larger than that of the small mass neutron star.

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https://www.actaphys.uj.edu.pl/R/44/2/211/pdf

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https://www.actaphys.uj.edu.pl/R/44/2/211

Multicritical Point in the One-dimensional Quantum Compass Model

Acta Phys. Pol. B **44**, 221 (2013)

page 221 •

abstract

The one-dimensional spin-1/2 quantum compass model is considered. There is a multicritical point in the ground state magnetic phase diagram of the model. By using the Jordan–Wigner transformation the diagonalized Hamiltonian is obtained and analytic expressions for the spin–spin correlation functions are determined at the multicritical point. On the other hand, the critical exponent of the energy gap in the vicinity of the multicritical point is calculated by a practical finite size scaling approach.

direct link to the full text (pdf)

https://www.actaphys.uj.edu.pl/R/44/2/221/pdf

link to the articles list

https://www.actaphys.uj.edu.pl/R/44/2/221

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