27 research outputs found
Double Lepton Polarization in Decay in the Standard Model with Fourth Generations Scenario
This study investigates the influence of the fourth generation quarks on the
double lepton polarizations in \Lambda_b --> \Lambda \ell^+ \ell^- decay by
taking |V^\ast_{t's}V_{t'b}|= 0.005,0.01,0.02,0.03 with phase
\{60^\circ,90^\circ,120^\circ\}. We will try to obtain a constrain on the mass
of the 4th generation top like quark t', which is consistent with the $b-->
s\ell^+\ell^- rate . With the above mentioned parameters, we will try to show
that the double lepton(muon, tau) polarizations are quite sensitive to the
existence of fourth generation. It can serve as a good tool to search for new
physics effects, precisely, to search for the fourth generation quarks(t', b')
via its indirect manifestations in loop diagrams.Comment: 36 pages, 33 figure
Form factors and decay rate of decays in the QCD sum rules
Rare exclusive decays are analyzed in
the framework of the three--point QCD sum rules approach. The two gluon
condensate corrections to the correlation function are included and the form
factors of this transition are evaluated. Using the form factors, the decay
width and integrated decay rate for these decays are also calculated.Comment: 17 pages, 3 figure
Exclusive B \rar \rho \ell^+ \ell^- Decay in the Standard Model with Fourth--Generation
We investigate the influence of the fourth generation of quarks on the
branching ratio, the CP-asymmetry and the polarization asymmetries in B \rar
\rho \ell^+ \ell^- decay. Taking with phase about
, which is consistent with the of the CKM and the
mixing parameter , we obtain that for both ()
channels the branching ratio is increased and the magnitude of CP-asymmetry and
polarization asymmetries decreased by the mass and mixing parameters of the 4th
generation of quarks . These results can serve as a good tool to search for new
physics effects, precisely, to search for the fourth generation of quarks( via its indirect manifestations in loop diagrams.Comment: 17 pages, 7 figure
CP-Conserving Unparticle Phase Effects on the Unpolarized and Polarized Direct CP Asymmetry in Transition
We examine the unparticle CP-conserving phase effects on the direct CP
asymmetry for both polarized and unpolarized lepton in the inclusive transition, where the flavor changing neutral currents are
forbidden at tree level but are induced by one-loop penguin diagrams. The
averaged polarized and unpolarized CP asymmetries depict strong dependency on
the unparticle parameters. In particular, a sizable discrepancy corresponding
to the standard model is achieved when the scale dimension value is 1. We see that the unparticle stuff significantly enhances, suppresses or
changes the sign of the CP asymmetry depending on the definite value of the
scaling dimension d_{\UP}. Especially, when d_{\UP}\sim 1.1 the CP
asymmetries vanish.Comment: 10 figures, PRD Published versio
A monte carlo approach to calculate the production prerequisites of124I radioisotope towards the activity estimation
The Monte Carlo simulation code MCNPX has been used to simulate the production of124I by124,125Te(p, xn) and123,124Te(d, xn) reactions to form high activity124I. For this reason, the TALYS-1.8 and ALICE/ASH codes were used to calculate the reaction cross-section. The optimal energy range of projectile is selected for this production by identifying the maximum cross-section and the minimum impurity due to other emission channels. Target geometry is designed by SRIM code based on stopping power calculations with identical dimensions as the experimental data. The thick target yield of reactions is predicted because of the excitation functions and stopping power. All of the prerequisites obtained from the above interfaces are adjusted in MCNPX code and the production process is simulated according to benchmark experiments. Thereafter, the energy distribution of proton in targets, the amount of residual nuclei during irradiation, were calculated. The results are in good agreement with the reported data, thus confirming the usefulness and accuracy of MCNPX as a tool for the optimization of other radionuclides production. Based on the results, the124Te(p, n)124I process seems to be the most likely candidate to produce the124I in low-energy cyclotrons. © 2018, Vinca Inst Nuclear Sci. All rights reserved
Analysis of the B --> \pi \ell^+ \ell^- Decay in the Standard Model with Fourth Generation
We investigate the influence of the fourth generation quarks on the branching
ratio and the CP-asymmetry in B -->\pi \ell^+ \ell^- decay. Taking the
|V_{t'd}V_{t'b}| ~ 0.001 with phase about 10 degree, which is consistent with
the sin2\phi_1 of the CKM and the B_d mixing parameter \Delta m_{B_d}, we
obtain that for both muon and tau channels the branching ratio, the magnitude
of CP-asymmetry and lepton polarization depict strong dependency on the 4th
generation quarks mass and mixing parameters. These results can serve as a good
tool to search for new physics effects, precisely, to search for the fourth
generation quarks( via its indirect manifestations in loop diagrams.Comment: 17 pages, 8 figure
Analysis of \Lambda_b \rar \Lambda \ell^+ \ell^- transition in SM4 using form factors from Full QCD
Using the responsible form factors calculated via full QCD, we analyze the
transition in the standard
model containing fourth generation quarks (SM4). We discuss effects of the
presence of fourth family quark on related observables like branching
ratio, forward-backward asymmetry, baryon polarization as well as double lepton
polarization asymmetries. We also compare our results with those obtained in
the SM as well as with predictions of the SM4 but using form factors calculated
within heavy quark effective theory. The obtained results on branching ratio
indicate that the transition
is more probable in full QCD comparing to the heavy quark effective theory. It
is also shown that the results on all considered observables in SM4 deviate
considerably from the SM predictions when .Comment: 22 Pages and 21 Figure
The Effects of Fourth Generation on the double Lepton Polarization in B \rar K \ell^+ \ell^- decay
This study investigates the influence of the fourth generation quarks on the
double lepton polarizations in B \rar K \ell^+ \ell^- decay. Taking
|V_{t's}V_{t'b}|\sim \{0.01-0.03\} with phase about 100^\circ, which is
consistent with the b\to s\ell^+\ell^- rate and the B_s mixing parameter Delta
m_{B_s}$, we obtain that the double lepton(muon and tau) polarizations are
quite sensitive to the existence of fourth generation. It can serve as a good
tool to search for new physics effects, precisely, to indirect search for the
fourth generation quarks(t', b').Comment: 30 pages, 27 figure
Differential branching fraction and angular analysis of decays
The differential branching fraction of the rare decay is measured as a function of , the
square of the dimuon invariant mass. The analysis is performed using
proton-proton collision data, corresponding to an integrated luminosity of 3.0
\mbox{ fb}^{-1}, collected by the LHCb experiment. Evidence of signal is
observed in the region below the square of the mass. Integrating
over 15 < q^{2} < 20 \mbox{ GeV}^2/c^4 the branching fraction is measured as
d\mathcal{B}(\Lambda^{0}_{b} \rightarrow \Lambda \mu^+\mu^-)/dq^2 = (1.18 ^{+
0.09} _{-0.08} \pm 0.03 \pm 0.27) \times 10^{-7} ( \mbox{GeV}^{2}/c^{4})^{-1},
where the uncertainties are statistical, systematic and due to the
normalisation mode, , respectively.
In the intervals where the signal is observed, angular distributions are
studied and the forward-backward asymmetries in the dimuon ()
and hadron () systems are measured for the first time. In the
range 15 < q^2 < 20 \mbox{ GeV}^2/c^4 they are found to be A^{l}_{\rm FB} =
-0.05 \pm 0.09 \mbox{ (stat)} \pm 0.03 \mbox{ (syst)} and A^{h}_{\rm FB} =
-0.29 \pm 0.07 \mbox{ (stat)} \pm 0.03 \mbox{ (syst)}.Comment: 27 pages, 10 figures, Erratum adde