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Josip Trampetic

Publications and source records attributed to Josip Trampetic.

36 records · Page 2Linked to original sources
arXiv2012

Photon-neutrino interaction in theta-exact covariant noncommutative model: Phenomenology and Quantum properties*

We construct the theta-exact covariant noncommutative (NC) model and obtain various closed constraints on the NC scale (Lambda_NC) from inelastic neutrino-nucleon scatterings (nu N -> nu+X), from plasmon decay into neutrino pair (gamma_pl -> bar nu + nu), from the BBN nucleosynthesis and from the reheating phase after inflation, respectively. We have have found neutrino two-point function in a closed form. It shows decoupling of the UV divergent term from softened UV/IR mixing term and from the finite terms as well. We show that problematic UV divergent and UV/IR mixing terms vanish for a certain choice of the noncommutative parameter theta which preserves unitarity. We find non-perturbative modifications of the neutrino dispersion relations which are assymptotically independent of the scale of noncommutativity in both the low and high energy limits and may allow superluminal propagation.

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arXiv2011

Constraining noncommutative field theories with holography

An important window to quantum gravity phenomena in low energy noncommutative (NC) quantum field theories (QFTs) gets represented by a specific form of UV/IR mixing. Yet another important window to quantum gravity, a holography, manifests itself in effective QFTs as a distinct UV/IR connection. In matching these two principles, a useful relationship connecting the UV cutoff $Λ_{\rm UV}$, the IR cutoff $Λ_{\rm IR}$ and the scale of noncommutativity $Λ_{\rm NC}$, can be obtained. We show that an effective QFT endowed with both principles may not be capable to fit disparate experimental bounds simultaneously, like the muon $g-2$ and the masslessness of the photon. Also, the constraints from the muon $g-2$ preclude any possibility to observe the birefringence of the vacuum coming from objects at cosmological distances. On the other hand, in NC theories without the UV completion, where the perturbative aspect of the theory (obtained by truncating a power series in $ Λ_{\rm NC}^{-2}$) becomes important, a heuristic estimate of the region where the perturbative expansion is well-defined $E/ Λ_{\rm NC} \lesssim 1$, gets affected when holography is applied by providing the energy of the system $E$ a $Λ_{\rm NC}$-dependent lower limit. This may affect models which try to infer the scale $Λ_{\rm NC}$ by using data from low-energy experiments.

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arXiv2009

Constraining spacetime noncommutativity with primordial nucleosynthesis

We discuss a constraint on the scale $Λ_{\rm NC}$ of noncommutative (NC) gauge field theory arising from consideration of the big bang nucleosynthesis (BBN) of light elements. The propagation of neutrinos in the NC background described by an antisymmetric tensor $θ^{μν}$ does result in a tree-level vector-like coupling to photons in a generation-independent manner, raising thus a possibility to have an appreciable contribution of three light right-handed (RH) fields to the energy density of the universe at nucleosynthesis time. Considering elastic scattering processes of the RH neutrinos off charged plasma constituents at a given cosmological epoch, we obtain for a conservative limit on an effective number of additional doublet neutrinos, $ΔN_ν=1$, a bound $Λ_{\rm NC} \stackrel{>}{\sim}$ 3 TeV. With a more stringent requirement, $ΔN_ν\lesssim 0.2$, the bound is considerably improved, $Λ_{\rm NC} \stackrel{>}{\sim} 10^3$ TeV. For our bounds the $θ$-expansion of the NC action stays always meaningful, since the decoupling temperature of the RH species is perseveringly much less than the inferred bound for the scale of noncommutativity.

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arXiv2009

Enveloping algebra Noncommutative SM: Renormalisability and High Energy Physics Phenomenology

In this talk we discuss enveloping algebra based noncommutative gauge field theory, constructed at the first order in noncommutative parameter theta, as an effective, anomaly free theory, with one-loop renormalizable gauge sector. Limits on the scale of noncommutativity parameter Lambda_NC, via related phenomenology and associated experiments, are analyzed and a firm bound to the scale of the noncommutativity is set around few TeV's.

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arXiv2008

Dark consequences from light neutrino condensations

In this paper we discuss light neutrino dipole moments, computed in the neutrino-mass extended standard model (SM), as a possible source for neutrino condensates which may cause cosmological constant observed today.

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arXiv2008

Renormalizability and Phenomenology of theta-expanded Noncommutative Gauge Field Theory

In this article we consider theta-expanded noncommutative gauge field theory, constructed at the first order in noncommutative parameter theta, as an effective, anomaly free theory, with one-loop renormalizable gauge sector. Related phenomenology with emphasis on the standard model forbidden decays, is discussed. Experimental possibilities of Z -> gamma gamma decay are analyzed and a firm bound to the scale of the noncommutativity parameter is set around few TeV's.

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arXiv2007

Remarks on the 2nd order Seiberg-Witten maps

In this report, we discuss the Seiberg-Witten maps up to the second order in the noncommutative parameter $θ$. They add to the recently published solutions in [1]. Expressions for the vector, fermion and Higgs fields are given explicitly.

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arXiv2007

Non-commutative SU(N) gauge theories and asymptotic freedom

In this paper we analyze the one-loop renormalization of the $θ$-expanded $\rm SU(N)$ Yang-Mills theory. We show that the {\it freedom parameter} $a$, key to renormalization, originates from higher order non-commutative gauge interaction, represented by a higher derivative term $ b h θ^{μν}\hat F_{μν}\star\hat F_{ρσ}\star\hat F^{ρσ}$. The renormalization condition fixes the allowed values of the parameter $a$ to one of the two solutions: $a=1$ or $a=3$, i.e. to $b=0$ or to $b=1/2$, respectively. When the higher order interaction is switched on, ($a=3$), pure non-commutative SU(N) gauge theory at first order in $θ$-expansion becomes one-loop renormalizable for various representations of the gauge group. We also show that, in the case $a=3$ and the adjoint representation of the gauge fields, the non-commutative deformation parameter $h$ has to be renormalized and it is asymptotically free.

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arXiv2007

Signal for space-time noncommutativity: the Z -> gamma gamma decay in the renormalizable gauge sector of the theta-expanded NCSM

We propose the Z -> gamma gamma decay, a process strictly forbidden in the standard model, as a signal suitable for the search of noncommutativity of coordinates at very short distances. We compute the Z -> gamma gamma partial widthin the framework of the recently proposed renormalizable gauge sector of the noncommutative standard model. The one-loop renormalizability is obtained for the model containing the usual six representations of matter fields of the first generation. Even more, the noncommutative part is finite or free of divergences, showing that perhaps new interaction symmetry exists in the noncommutative gauge sector of the model. Discovery of such symmetry would be of tremendous importance in further search for the violation of the Lorentz invariance at very high energies. Experimental possibilities of Z -> gamma gamma decay are analyzed and a firm bound to the scale of the noncommutativity parameter is set around 1 TeV.

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arXiv2006

The one-loop renormalization of the gauge sector in the noncommutative standard model

In this paper we construct a version of the standard model gauge sector on noncommutative space-time which is one-loop renormalizable to first order in the expansion in the noncommutativity parameter $θ$. The one-loop renormalizability is obtained by the Seiberg-Witten redefinition of the noncommutative gauge potential for the model containing the usual six representations of matter fields of the first generation.

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arXiv2005

Charmless and Strangless Nonleptonic B Decays

Decay rates of the B-meson are studied through charmless and strangless transitions into pi, rho, omega and gamma systems. The important features of these modes are their clean signatures. The CLEO II collaboration has recently reported the value BR(B^0 --> pi^+ pi^-) = (1.3_{-0.6}^{+0.8} +/- 0.2)x10^{-5}. This value test our approach to nonleptonic B-decays within the standard model (SM). Since B --> gamma gamma is far beyond our experimental reach, we believe that the correct determination of the order of magnitude ~10^{-10} for BR(B --> gamma gamma) provides the most reliable value needed at this moment. The most recent experimental report by the CLEO collaboration on BR(B --> K* gamma) = (4.5 +/- 1.5 +/- 0.9)x10^{-5} represents a confirmation of our SM prediction for the B --> K* gamma decay. This experimental result, despite of its great importance for the SM and the physics beyond the SM, enables us to predict the value BR(B --> rho gamma) ~ (3.5 +/- 3.3)x10^{-6}.

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arXiv2004

Neutrino dipole moments and charge radii in noncommutative space-time

In this paper we obtain a bound $Λ_{\rm NC} < 150$ TeV on the scale of space-time noncommutativity considering photon-neutrino interactions. We compute "star-dipole moments" and "star-charge radii" originating from space-time noncommutativity and compare them with the dipole moments calculated in the neutrino-mass extended standard model (SM). The computation depends on the nature of the neutrinos, Dirac versus Majorana, their mass and the energy scale. We focus on Majorana neutrinos. The "star-charge radius" is found to be $r^* = \sqrt{|< r^2_ν>_{\rm NC}|} =|3\sum_{i=1}^3 (θ^{0i})^2|^{1/4} < 1.6 \times 10^{-19}$ cm at $Λ_{\rm NC} = 150$ TeV.

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arXiv2003

The photon-neutrino interaction in non-commutative gauge field theory and astrophysical bounds

In this letter we propose a possible mechanism of left- and right-handed neutrino couplings to photons, which arises quite naturally in non-commutative gauge field theory. We estimate the predicted additional energy-loss in stars induced by space-time non-commutativity. The usual requirement that any new energy-loss mechanism in globular stellar clusters should not excessively exceed the standard neutrino losses implies a scale of non-commutative gauge theory above the scale of weak interactions.

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arXiv2003

Rare and forbidden decays

In these lectures I first cover radiative and semileptonic B decays, including the QCD corrections for the quark subprocesses. The exclusive modes and the evaluation of the hadronic matrix elements, i.e. the relevant hadronic form factors, are the second step. Small effects due to the long-distance, spectator contributions, etc. are discussed next. The second section we started with non-leptonic decays, typically $B \to ππ, Kπ, ρπ,...$ We describe in more detail our prediction for decays dominated by the $b\to s η_c$ transition. Reports on the most recent experimental results are given at the end of each subsection. In the second part of the lectures I discuss decays forbidden by the Lorentz and gauge invariance, and due to the violation of the angular moment conservation, generally called the Standard Model-forbiden decays. However, the non-commutative QED and/or non-commutative Standard Model (NCSM), developed in a series of works in the last few years allow some of those decay modes. These are, in the gauge sector, $Z\to γγ, gg$, and in the hadronic sector, flavour changing decays of the type $K\to πγ$, $B\to Kγ$, etc. We shall see, for example, that the flavour changing decay $D^+_s\to π^+ γ$ dominates over other modes, because the processes occur via charged currents, i.e. on the quark level it arises from the point-like photon $\times$ current $\times$ current interactions. In the last section we present the transition rate of ``transverse plasmon'' decay into a neutrino--antineutrino pair via noncommutative QED, i.e. $γ_{\rm pl}\to ν\barν$. Such decays gives extra contribution to the mechanism for the energy loss in stars.

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arXiv1995

Long Distance Contributions to Penguin Processes $b\rightarrow sγ$ and $b\rightarrow d γ$

We consider the long distance contributions to inclusive penguin processes through processes like $b\rightarrow s V$ and $b\rightarrow d V$ where $V$ are $^3S_1(c\bar c)$ states $ψ_i$ in the former case and include $ρ$, $ω$ for the latter case. We carefully examine vector dominance for $\bar c c$ states, and conclude that there is a large suppression of $ψ\sim γ$ transition when $ψ$ is at $q^2 = 0$. The long distance effects can be at most 10\% in both the amplitudes for $b\rightarrow sγ$ and $b\rightarrow d γ$. Although the long distance contributions are small, the ratio $BR(b\rightarrow dγ)/BR(b \rightarrow s γ) = |V_{td}/V_{ts}|^2$ does not hold due to significant $u$ and $c$ loop contributions to the short distance $b\rightarrow dγ$ amplitudes .

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arXiv1994

Exclusive and Semi-Inclusive B Decays Based on \hspace{0.3cm} b $\rightarrow$ s \hspace{0.01cm}$η_c$ \hspace{0.3cm} Transition

We calculate the semi-inclusive processes B $\rightarrow X_{s} η_c$ and relate it to B $\rightarrow X_{s} ψ$ in next to leading order QCD, and show how it can be used to determine an accurate value of $f_{η_{c}}$. The exclusive modes B $\rightarrow$ K$η_c$ and B $\rightarrow$ K$ψ$ also yield similar results, whereas B $\rightarrow$ K$^*η_c$ and B $\rightarrow$ K$^*ψ$ can provide valuable information on hadronic form factors. We also estimate the branching ratios and the ratios of exclusive to inclusive decay modes dominated by $b \rightarrow s\e$.

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