arXiv subjects

A. B. Santra

Publications and source records attributed to A. B. Santra.

7 recordsLinked to original sources

arXiv2001

Maximum mass of neutron stars with a quark core

Massive neutron stars (NS) are expected to possess a quark core. While the hadronic side of the NS equation of state (EOS) can be considered well established, the quark side is quite uncertain. While calculating the EOS of hadronic matter we have used the Brueckner-Bethe-Goldstone formalism with realistic two-body and three-body forces, as well as a relativistic mean field model. For quark matter we employ the MIT bag model constraining the bag constant by exploiting the recent experimental results obtained at CERN on the formation of a quark-gluon plasma. We calculate the structure of NS interiors with the EOS comprising both phases, and we find that the NS maximum masses fall in a relatively narrow interval, $1.45 M_\odot \leq M_{\rm max} \leq 1.65 M_\odot$, near the lower limit of the observational range.

astro-ph↗

arXiv1998

The elementary p(p,p'π^{+})n reaction

A detailed study of the elementary p(p,p$'π^{+}$)n reaction is presented using the delta isobar model. In this model, in the first step one of the two protons in the initial state gets excited to $Δ$. This, in the second step, decays into a nucleon and a pion. For the $pp \to NΔ$ step the parametrized form of the DWBA t-matrix of Jain and Santra, which reproduces most of the available data on $pp \to nΔ^{++}$, is used. The cross-sections studied include the outgoing proton momentum spectra in coincidence with the pion, the outgoing pion momentum spectra and the integrated total cross-section. We find that all the calculated numbers are in good agreement with the corresponding measured cross sections.

nucl-th↗

arXiv1996

What are effective $a_1$ and $a_2$ in two-body hadronic decays of D and B mesons?

Through a specific example of two-body color-favored charm decay, $D_s ^+ \rightarrow ϕπ^+$, we illustrate how an effective and complex (unitarized) $a_1$, denoted by $a_1^{U,eff}$, may be defined such that it includes nonfactorized, annihilation and inelastic final state interaction (fsi) effects. The procedure can be generalized to color-suppressed processes to define an effective, and complex $a_2^{U,eff}$. We determine $|a_1^{U,eff}|$ and, where relevant, $|a_2^{U,eff}|$ for $D\rightarrow \bar{K}π, \bar{K} ρ, \bar{K}^{*} π, D_s^+ \rightarrow ηπ^+$, $η' π^+$, $ηρ^+ ,η' ρ^+$, and for $B^0 \rightarrow D^- π^+$ and $D^- ρ^+$ from the hadronic and semileptonic decay data.

hep-ph↗

arXiv1995

Nonfactorization in Hadronic Two-body Cabibbo-favored decays of D^0 and D^+

With the inclusion of nonfactorized amplitudes in a scheme with $N_c=3$, we have studied Cabibbo-favored decays of $D^0$ and $D^+$ into two-body hadronic states involving two isospins in the final state. We have shown that it is possible to understand the measured branching ratios and determined the sizes and signs of nonfactorized amplitudes required.

hep-ph↗

arXiv1995

Nonfactorization and the decays $D_s^+ \to ϕπ^+, ϕρ^+$ and $ϕl^+ ν_l$

In six chosen scenarios for the $q^2$ dependence of the form factors involved in $D_s^+ \rightarrow ϕ$ transition, we have determined the allowed domain of $x = A_2(0) / A_1(0)$ and $y = V(0)/A_1(0)$ from the experimentally measured ratios $R_{sl} = Γ(D_s^+ \rightarrow ϕl^+ ν_l)/Γ(D_s^+ \rightarrow ϕπ^+)$ and $R_h = Γ(D_s^+ \rightarrow ϕρ^+)/Γ(D_s^+ \rightarrow ϕπ^+)$ in a scheme that uses the $N_c =3$ value of the phenomenological parameter $a_1$ and includes nonfactorized contribution. We find that the experimentally measured values of $x$ and $y$ from semileptonic decays of $D_s^+$ favor solutions which have significant nonfactorized contribution, and, in particular, $R_{sl}$ favors solutions in scenarios where $A_1(q^2)$ is either flat or decreasing with $q^2$.

hep-ph↗

arXiv1995

Nonfactorization and Color-Suppressed $B \to ψ(ψ(2S))+K(K^*)$ Decays

Using $N_c=3$ value of the parameter $a_2=0.09$ but including a modest nonfactorized amplitude, we show that it is possible to understand all data, including polarization, for color-suppressed $B\toψ(ψ(2S))+K(K^*) $ decays in all commonly used models of form factors. We show that for $B\toψ+K$ decay one can define an effective $ a_2$, which is process-dependent and, in general, complex; but it is not possible to define an effective $a_2$ for $B\toψ+K^* $ decay. We also explain why nonfactorized amplitudes do not play a significant role in color-favored B decays.

hep-ph↗

arXiv1994

Probing Factorization in Color-Suppressed $B \rightarrow ψ(2S) + K(K^*)$ Decay

In order to probe the factorization hypothesis in color-suppressed $B \rightarrow ψ(2S) + K (K^*)$ decays we have studied three ratios: $ R \equiv B (B \rightarrow ψK) / B (B \rightarrow ψ(2S) K)$, $ R' \equiv B (B \rightarrow ψK^*) / B (B \rightarrow ψ(2S) K^*)$ and $ P_L^\prime \equiv Γ_L (B \rightarrow ψ(2S) K^*)/Γ(B \rightarrow ψ(2S) K^*)$ in several scenarios for the $ q^2$-dependence of the form factors involved. We find that measurements of R and $R' $, which exist, do not yield scenario-independent tests of factorization. However, the predicted range of $ P_L^\prime$ in all scenarios lies in a narrow range, $ 0.50 {\ \lower-1.2pt\vbox{\hbox{\rlap{$<$}\lower5pt\vbox{\hbox{$\sim$}}}}\ } P_L^\prime \leq 0.67$, and could test factorization.

hep-ph↗