Rare B_s -> \gamma \nu \bar{\nu} decay with polarized photon and new physics effects

Using the most general, model independent effective Hamiltonian, the rare B_s ->\gamma \nu \bar{\nu} decay with polarized photon is studied. The sensitivity of the branching ratio and photon polarization to the new Wilson coefficients are investigated. It is shown that these physical observables are sensitive to the vector and tensor type interactions, which would be useful in search of new physics.Comment: 9 pages, 5 figure

QCD Sum Rules study of meson-baryon sigma terms

The pion-baryon sigma terms and the strange-quark condensates of the octet and the decuplet baryons are calculated by employing the method of quantum chromodynamics (QCD) sum rules. We evaluate the vacuum-to-vacuum transition matrix elements of two baryon interpolating fields in an external isoscalar-scalar field and use a Monte Carlo-based approach to systematically analyze the sum rules and the uncertainties in the results. We extract the ratios of the sigma terms, which have rather high accuracy and minimal dependence on QCD parameters. We discuss the sources of uncertainties and comment on possible strangeness content of the nucleon and the Delta.Comment: 17 pages, 10 figures, to be published in Phys. Rev.

Standard Model CP violation in B->X_d \ell^+\ell^- decays

We investigate the CP violating asymmetry, the forward backward asymmetry and the CP violating asymmetry in the forward-backward asymmetry for the inclusive B->X_d \ell^+\ell^- decays for the \ell=e,\mu \tau channels in the standard model. It is observed that these asymmetries are quite sizable and B->X_d \ell^+\ell^- decays seem promising for investigating CP violation.Comment: 13 pages, 6 figure

Quantal description of nucleon exchange in a stochastic mean-field approach

The nucleon exchange mechanism is investigated in central collisions of symmetric heavy ions in the basis of the stochastic mean-field approach. Quantal diffusion coefficients for nucleon exchange are calculated by including non-Markovian effects and shell structure. Variances of fragment mass distributions are calculated in central collisions of Ca-40 + Ca-40, Ca-48 + Ca-48, and N-56 i+ Ni-56 systems

Ağır-iyon reaksiyonlarının stokastik ortalama-alan kuramı çerçevesinde incelenmesi

TÜBİTAK MFAG15.10.2015Bu projede, ağır-iyon derin-inelastik çarpışmalarında mermi ve hedef çekirdekler arasında nükleon alış-verişi ile ilgili transport katsayıları için stokastik ortalama- alan kuramı (SOA) çerçevesinde yarı-klasik ve hafıza etkilerini içeren kuantal hesaplamalar yapıldı. Simetrik ve proton/nötron bakımından asimetrik sistemlerin füzyon potansiyel bariyer değerlerinin hemen altındaki enerjilerde merkezi ve merkezi olmayan çarpışmaları göz önüne alındı. Ağır-iyonların merkezi çarpışmaları için türetilen ve simetrik sistemlerde test edilen kuantum mekaniksel hesaplar, asimetrik sistemlere ve merkezi olmayan çarpışmalara genişletildi. Benzer şekilde, nükleon alışveriş difüzyon katsayısının analitik ifadeleri, simetrik ve asimetrik ağır-iyonların merkezcil olmayan çarpışmaları için hafıza etkilerini de içerecek şekilde kuantum mekaniksel olarak türetildi. Proje kapsamında, ağır-iyon derin-inelastik çarpışma sonrası ayrışan çekirdeklerin proton ve nötron difüzyon katsayıları, kütle dağılımlarının varyansları ile toplam difüzyon katsayısı ve toplam nükleon kütle dağılımının varyansı çeşitli sistemler için hesaplandı. Proje iş paketlerinde öngörülen ve aşağıdaki verilen tüm çalışmalar tamamlandı. 1) Simetrik ve nötron/proton bakımından asimetrik atom çekirdeklerinin düşük- enerjili derin-inelastik merkezcil transport katsayılarının kuantal olarak hesaplanması ve daha önce yapılan yarı-klasik hesaplarla karşılaştırılması yapıldı. 2) Simetrik ve asimetrik atom çekirdeklerinin düşük-enerjili derin-inelastik merkezcil olmayan çarpışmalarında toplu değişkenlerin tanımlanması için gerekli olan pencere dinamığının zamana bağlı Hartree-Fock programına gerekli eklemeler yapılarak, proton ve nötron alış-verişi ile ilgili difüzyon katsayılarının kuantal olarak hesaplanması, bu katsayıları kullanarak ayrışan çekirdeklerin proton ve nötron dağılımlarının ortalama değerlerinin ve varyanslarının hesaplanması yapıldı. 3) Simetrik ve nötron/proton bakımından asimetrik atom çekirdeklerinin düşük- enerjili derin-inelastik merkezcil olmayan çarpışmalarında nükleon alış- verişine dayalı transport katsayılarının kuantal olarak hesaplanması, enerji disipasyon ve salınım mekanizmasının incelenmesi yapıldı. 4) Ağır çekirdekler arası nükleon transferi için transport katsayılarının hafıza etkilerini yaklaşık olarak hesaba katarak kuantal hesaplanması için yeni bir yöntem geliştirildi. 5) Yarı-fisyon reaksiyonlarının difüzyon menizmasıyla incelenmesi hesapları yapıldı

The effects of non-standard Z couplings on the lepton polarizations in B_s to \gamma \ell^+ \ell^- decays

The fact that the measured B to \pi \pi, \pi K branching ratios exhibit puzzling patterns has received a lot of attention in the literature and motivated the formulation of a series of new physics scenarios with enhanced Z-penguins. In this work, we analyze the effect of such an enhancement on the lepton polarization asymmetries of B_s to \gamma \ell^+ \ell^- decays by applying the results of a specific scenario for the solution of ``B to \pi K puzzle''.Comment: 12 pages, 6 figure

Charm and Bottom Semileptonic Decays

We review the present status of theoretical attempts to calculate the semileptonic charm and bottom decays and then present a calculation of these decays in the light--front frame at the kinematic point $q^2=0$. This allows us to evaluate the form factors at the same value of $q^2$, even though the allowed kinematic ranges for charm and bottom decays are very different. Also, at this kinematic point the decay is given in terms of only one form factor $A_{0}(0)$. For the ratio of the decay rates given by the E653 collaboration we show that the determination of the ratio of the Cabibbo--Kobayashi--Maskawa (CKM) matrix elements is consistent with that obtained from the unitarity constraint. At present, though, the unitarity method still has greater accuracy. Since comparisons of the semileptonic decays into $\rho$ and either electrons or muons will be available soon from the E791 Fermilab experiment, we also look at the massive muon case. We show that for a range of $q^2$ the $SU(3)_F$ symmetry breaking is small even though the contributions of the various helicity amplitudes becomes more complicated. For $B$ decays, the decay $B \rightarrow K^{*} \ell \bar{\ell}$ at $q^2=0$ involves an extra form factor coming from the photon contribution and so is not amenable to the same kind of analysis, leaving only the decay $B \rightarrow K^{*}\nu \bar{\nu}$ as a possibility. As the mass of the decaying particle increases we note that the $SU(3)$ symmetry becomes badly broken at $q^2=0$.Comment: Latex, 19 pages, two figures are attached, a minor change in the manuscript related to thi

The exclusive B→πℓ+ℓ−B\to \pi \ell^+ \ell^- and B→ρℓ+ℓ−B\to \rho \ell^+ \ell^- decays in the general two Higgs doublet model

We study the differential branching ratio, branching ratio and the forward-backward asymmetry for the exclusive $B \to \pi \ell^+ \ell^-$ and $B \to \rho \ell^+ \ell^-$ decays in the general two Higgs doublet model including the neutral Higgs boson effects. We analyze the dependencies of these quantities on the neutral Higgs boson contributions and the other model parameters. We observe that two Higgs doublet model with the neutral Higgs boson exchanges gives quite sizable contributions to these observables for both channels we consider. Since the neutral Higgs boson exchanges are the only source of the forward-backward asymmetry for $B \to \pi \tau^+ \tau^-$ decay, which is at the order of magnitude $1-10$, measurement of this observable is promising to determine the neutral Higgs boson effects.Comment: 27 pages, 18 eps figures, requires JHEP3.cls (included), replaced with the version to appear in JHE

The exclusive B−>(K,K∗)ℓ+ℓ−B -> (K, K^*) \ell^+ \ell^- decays in a CP softly broken two Higgs doublet model

We study the differential branching ratio, forward-backward asymmetry, CP-violating asymmetry, CP-violating asymmetry in the forward-backward asymmetry and polarization asymmetries in the $B -> K \ell^+ \ell^-$ and $B -> K^* \ell^+ \ell^-$ decays in the context of a CP softly broken two Higgs doublet model. We analyze the dependencies of these observables on the model parameters by paying a special attention to the effects of neutral Higgs boson (NHB) exchanges and possible CP violating effects. We find that NHB effects are quite significant for both decays. A combined analysis of above-mentioned observables seems to be very promising as a testing ground for new physics beyond the SM, especially for the existence of the CP-violating phase in the theory.Comment: 23 pages, 26 eps figures, version to appear in Nucl. Phys.

The exclusive Lambda(b) Lambda l(+) l(-) decay in the general two Higgs doublet model

The exclusive Lambda(b) -> Lambda l(+)l decay is analysed in the model III version of the two Higgs doublet model. We especially studied the branching ratio and the forward-backward asymmetry of this process and investigated the sensitivity of these physical observable to the model parameters. We have found that they are highly sensitive to new physics and hence provide powerful probe of the SM