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Register a new userUnparticle effects in Supernovae cooling
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Prasanta Kumar Das
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Recently H. Georgi suggested that a scale invariant unparticle ${mathcal{U}}$ sector with an infrared fixed point at high energy can couple with the SM matter via a higher-dimensional operator suppressed by a high cut-off scale. Intense phenomenological search of this unparticle sector in the collider and flavour physics context has already been made. Here we explore its impact in cosmology, particularly its possible role in the supernovae cooling. We found that the energy-loss rate (and thus the cooling) is strongly dependent on the effective scale LdaU and the anomalous dimension dU of this unparticle theory.
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In this work we study the flavor changing neutral current(FCNC) decays of the top quark, $tto cgamma$ and $tto c g$. The Standard Model, predictions for the branching ratios of these decays are about $sim 5times 10^{-14}$, and $sim 1times 10^{-12}$, respectively. The recent study presented by the ATLAS Collaboration gives a sensitivity on these branching ratios about $sim 10^{-5}$ at $%95$ C.L. The parameter space of $lambda$, $Lambda$, and $d$ where the branching ratios of $tto cgamma$ and $tto c g$ decays exceed these predictions is obtained.
Rare (t -> c g g) decay can only appear at loop level in the Standard Model (SM), and naturally they are strongly suppressed. These flavor changing decays induced by the mediation of spin-0 and spin-2 unparticles, can appear at tree level in unparticle physics. In this work the virtual effects of unparticle physics in the flavor-changing (t -> c g g) decay is studied. Using the SM result for the branching ratio of the (t -> c g g) decay, the parameter space of d_U and Lambda_U, where the branching ratio of this decay exceeds the one predicted by the SM, is obtained. Measurement of the branching ratio larger than 10^(-9) can give valuable information for establishing unparticle physics.
We study unparticle physics effects in (Lambda_b -> Lambda + missing energy) decay with polarized $Lambda_b$ and $Lambda$ baryons. The sensitivity of the branching ratio of this decay and polarizations of (Lambda_b) and (Lambda) baryons on the scale dimension d_U and effective cut-off parameter (Lambda_U) are discussed.
The mixing of $K^0-bar{K^0}$, $D^0-bar{D^0}$ and $B_{(s)}^0-bar{B^0_{(s)}}$ provides a sensitive probe to explore new physics beyond the Standard Model. The scale invariant unparticle physics recently proposed by Georgi can induce flavor-changing neutral current and contribute to the mixing at tree level. We investigate the unparticle effects on $B^0-bar{B^0}$ and $D^0-bar{D^0}$ mixing. Especially, the newly observed $D^0-bar{D^0}$ mixing sets the most stringent constraints on the coupling of the unparticle to quarks.
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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