The exclusive B_s\rightarrow \phi \ell^+ \ell^- decay in the two Higgs doublet models

We study the differential branching ratio, the branching ratio and the forward-backward asymmetry for exclusive decay in the two Higgs doublet model. We analyze the dependences of these quantities on the model parameters and show that these observables are highly sensitive to new physics and hence may provide a powerful probe of the SM and beyond. Received: 27 March 2002 / Revised version: 3 July 2002 / Published online: 20 September 2002 RID="a" ID="a" e-mail: gurerk@newton.physics.metu.edu.tr RID="b" ID="b" e-mail: gsevgur@metu.edu.tr     

General analysis of CP-violation in polarized $b \rightarrow d \ell^ + \ell^-$ decay

The CP-violating asymmetries in the decay, when one of the leptons is polarized, is investigated using the most general form of the effective Hamiltonian. The sensitivity of the CP-violating asymmetries to the new Wilson coefficients is studied.Received: 23 August 2003, Published online: 4 November 2003     

The $Z \rightarrow \gamma \gamma,\;gg$ decays in the non-commutative standard model

On non-commutative spacetime, the standard model (SM) allows new, usually SM forbidden, triple gauge boson interactions to occur. In this letter we propose the SM strictly forbidden and decay modes coming from the gauge sector of the non-commutative standard model (NCSM) as a place where non-commutativity could be experimentally discovered. Received: 2 July 2002, Revised: 28 February 2003, Published online: 18 June 2003     

Study of the weak annihilation contributions in charmless $$\varvec{B_s\rightarrow VV}$$ decays

In this paper, in order to probe the spectator-scattering and weak annihilation contributions in charmless \(B_s\rightarrow VV\) (where V stands for a light vector meson) decays, we perform the \(\chi ^2\)-analyses for the endpoint parameters within the QCD factorization framework, under the constraints from the measured \(\bar{B}_{s}\rightarrow \) \(\rho ^0\phi \), \(\phi K^{*0}\), \(\phi \phi \) and \(K^{*0}\bar{K}^{*0}\) decays. The fitted results indicate that the endpoint parameters in the factorizable and nonfactorizable annihilation topologies are non-universal, which is also favored by the charmless \(B\rightarrow PP\) and PV (where P stands for a light pseudo-scalar meson) decays observed in previous work. Moreover, the abnormal polarization fractions \(f_{L,\bot }(\bar{B}_{s}\rightarrow K^{*0}\bar{K}^{*0})=(20.1\pm 7.0)\%,(58.4\pm 8.5)\%\) measured by the LHCb collaboration can be reconciled through the weak annihilation corrections. However, the branching ratio of \(\bar{B}_{s}\rightarrow \phi K^{*0}\) decay exhibits a tension between the data and theoretical result, which dominates the contributions to \(\chi _\mathrm{min}^2\) in the fits. Using the fitted endpoint parameters, we update the theoretical results for the charmless \(B_s\rightarrow VV\) decays, which will be further tested by the LHCb and Belle-II experiments in the near future.     

Saturation effects in pA \rightarrow dilepton and photon production

I discuss the inclusive dilepton/photon cross section for proton (quark)-nucleus collisions at high energies in the very forward rapidity region, predicting leading twist shadowing together with anomalous scaling behavior.Arrival of the final proofs: 22 March 2005PACS: 24.85. + p, 25.75.-q     

The radiative leptonic decays D^0 \to e^+ e^-\gamma,\mu^+\mu^-\gamma in the standard model and beyond

We present a calculation of the rare decay modes and in the framework of the standard model. For the short distance part we have derived QCD corrections to the Wilson coefficients involved, including C₉. The latter is found to be strongly suppressed by the corrections, leading to diminished values for the branching ratios in the 10^-10 range. Within SM the exclusive decays are dominated by long distance effects. Non-resonant contributions are estimated using heavy quark and chiral symmetries to be at the level of , compared to the contributions arising from , with . The total SM branching ratio is predicted to be in the range (1-. We also consider contributions coming from MSSM with and without R parity conservation. The effects from MSSM are significant only for the R parity violating case. Such contributions enhance the branching ratio to , based on appropriately allowed values for C₉ and C₁₀. This selects as a possible probe of new physics. Received: 25 October 2002 / Published online: 24 January 2003     

\mu\rightarrow e\gamma decay in the left-right supersymmetric model

We calculate the dipole amplitude for the decay and related processes in the left-right supersymmetric model when parity breaking occurs at a considerably large scale. The low-energy flavor violation in the model originates either from the nonvanishing remnants of the left-right symmetry in the slepton mass matrix or from the direct flavor changing lepton-slepton-neutralino interaction. The result is found to be large and already accessible with current experimental accuracy for supersymmetric masses not far above the electroweak scale. It also provides nontrivial constraints on the lepton mixing in the model. Received: 8 June 1998 / Published online: 15 October 1998