In the Randall-Sundrum model where the Standard Model fields are confined to the TeV brane located at the orbifold point $theta = pi$ and the gravity peaks at the Planck brane located at $theta = 0$, the stabilized modulus (radion) field is required
to stabilize the size of the fifth spatial dimension. It can be produced copiously inside the supernova core due to nucleon-nucleon bremstrahlung, electron-positron and plasmon-plasmon annihilations, which then subsequently decays to neutrino-antineutrino pair and take away the energy released in SN1987A explosion. Assuming that the supernovae cooling rate $dot{varepsilon} le 7.288times 10^{-27} rm{GeV}$, we find the lower bound on the radion vev $vphi sim 9.0$ TeV, 2.2 TeV and 0.9 TeV corresponding to the radion mass $m_phi = 5$ GeV, 20 GeV and 50 GeV, respectively.
We study the neutral Higgs boson pair production through $e^{+} e^{-}$ collision in the noncommutative(NC) extension of the standard model using the Seiberg-Witten maps of this to the first order of the noncommutative parameter $Theta_{mu u}$. This
process is forbidden in the standard model at the tree level with background space-time being commutative. After including the effects of earths rotation we analyse the time-averaged cross section of the pair production of Higgs boson (in the light of LEP II and LHC data) at the future Linear Collider which can be quite significant for the NC scale $Lambda$ lying in the range $0.3 - 1.0$ TeV. For the 125 GeV Higgs mass(the most promising value of Higgs mass as reported by LHC), we find the NC scale as $330 rm{GeV}$ $le Lambda le 660 rm{GeV}$ and using $m_h = 129(127.5) rm{GeV}$ (the lower threshold value of the excluded region of $m_h$ reported by ATLAS(CMS) collaborations of LHC), we find the bound on $Lambda$ as: (i) $339 (336) rm{GeV} le Lambda le 677 (670) rm{GeV}$ corresponding to the Linear Collider energy $E_{com} = 500 rm{GeV}$.
We study the muon pair production $ e^+ e^- to mu^+ mu^-$ in the framework of the non-minimal noncommutative(NC) standard model to the second order of the NC parameter $Theta_{mu u}$. The $mathcal{O}(Theta^2)$ momentum dependent NC interaction signif
icantly modifies the cross section and angular distributions which are different from the standard model. After including the effects of earths rotation we analyse the time-averaged and time dependent observables in detail. The time-averaged azimuthal distribution of the cross section shows siginificant departure from the standard model. We find strong dependence of the total cross section(time- averaged) and their distributions on the orientation of the noncommutative electric vector (${vec{Theta}}_E$). The periodic variation of the total cross-section with time over a day seems to be startling and can be thoroughly probed at the upcoming Linear Collider(LC).
We study the Higgs boson pair production through $e^+e^-$ collision in the noncommutative(NC) extension of the standard model using the Seiberg-Witten maps of this to the first order of the noncommutative parameter $Theta_{mu u}$. This process is fo
rbidden in the standard model with background space-time being commutative. We find that the cross section of the pair production of Higgs boson (of intermediate and heavy mass) at the future Linear Collider(LC) can be quite significant for the NC scale $Lambda$ lying in the range $0.5 - 1.0$ TeV. Finally, using the direct experimental(LEP II, Tevatron and global electro-weak fit) bound on Higgs mass, we obtain bounds on the NC scale as 665 GeV $le Lambda le 998$ GeV.
We study muon pair production $ e^+ e^- to mu^+ mu^-$ in the noncommutative(NC) extension of the standard model using the Seiberg-Witten maps of this to the second order of the noncommutative parameter $Theta_{mu u}$. Using $mathcal{O}(Theta^2)$ Fey
nman rules, we find the $mathcal{O}(Theta^4)$ cross section(with all other lower order contributions simply cancelled) for the pair production. The momentum dependent $mathcal{O}(Theta^2)$ NC interaction significantly modifies the cross section and angular distributions which are different from the commuting standard model. We study the collider signatures of the space-time noncommutativity at the International Linear Collider(ILC) and find that the process $ e^+ e^- to mu^+ mu^-$ can probe the NC scale $Lambda$ in the range $0.8 - 1.0$ TeV for typical ILC energy ranges.
We analyze the inclusive $b(c) to s(u) mu^+ mu^-$ and the exclusive $B(D^+) to K(pi^+) mu^+ mu^-$ flavour changing neutral current decays in the light of HyperCP boson $X^0$ of mass 214 MeV recently observed in the hyperon decay $Sigma^+ to p mu^+ mu
^-$. Using the branching ratio data of the above inclusive and exclusive decays, we obtain constraints on $g_1 (h_1)$ and $g_2 (h_2)$, the scalar and pseudo-scalar coupling constants of the $b-s-X^0 (c-u-X^0)$ vertices.
In large extra dimensional Kaluza-Klein (KK) scenario, where the usual Standard Model (SM) matter is confined to a 3+1-dimensional hypersurface called the 3-brane and gravity can propagate to the bulk (D=4+d, d being the number of extra spatial dimen
sions), the light graviton KK modes can be produced inside the supernova core due to the usual nucleon-nucleon bremstrahlung, electron-positron and photon-photon annihilations. This photon inside the supernova becomes plasmon due to the plasma effect. In this paper, we study the energy-loss rate of SN 1987A due to the KK gravitons produced from the plasmon-plasmon annihilation. We find that the SN 1987A cooling rate leads to the conservative bound $M_D$ > 22.9 TeV and 1.38 TeV for the case of two and three space-like extra dimensions.
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 phenomenologi
cal 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.
