Search results for "isospin"
showing 10 items of 264 documents
Nonquenched Isoscalar Spin-M1Excitations insd-Shell Nuclei
2015
Differential cross sections of isoscalar and isovector spin-M1 (0(+)→1(+)) transitions are measured using high-energy-resolution proton inelastic scattering at E(p)=295 MeV on (24)Mg, (28)Si, (32)S, and (36)Ar at 0°-14°. The squared spin-M1 nuclear transition matrix elements are deduced from the measured differential cross sections by applying empirically determined unit cross sections based on the assumption of isospin symmetry. The ratios of the squared nuclear matrix elements accumulated up to E(x)=16 MeV compared to a shell-model prediction are 1.01(9) for isoscalar and 0.61(6) for isovector spin-M1 transitions, respectively. Thus, no quenching is observed for isoscalar spin-M1 transi…
Measurements ofB→{π,η,η′}lνlBranching Fractions and Determination of|Vub|with Semileptonically TaggedBMesons
2008
We report measurements of branching fractions for the decays B-->Plnu_{l}, where P are the pseudoscalar charmless mesons pi;{-}, pi;{0}, eta and eta;{'}, based on 348 fb;{-1} of data collected with the BABAR detector, using B0 and B+ mesons found in the recoil of a second B meson decaying as B-->D;{(*)}lnu_{l}. Assuming isospin symmetry, we combine pionic branching fractions to obtain B(B;{0}-->pi;{-}l;{+}nu_{l})=(1.54+/-0.17_{(stat)}+/-0.09_{(syst)})x10;{-4}; we find 3.2sigma evidence of the decay B;{+}-->etal;{+}nu_{l} and measure its branching fraction to be (0.64+/-0.20_{(stat)}+/-0.03_{(syst)})x10;{-4}, and determine B(B;{+}-->eta;{'}l;{+}nu_{l})<0.47x10;{-4} to 90% confidence level. U…
Translationally invariant treatment of pair correlations in nuclei: I. Spin and isospin dependent correlations
1996
We study the extension of our translationally invariant treatment of few-body nuclear systems to heavier nuclei. At the same time we also introduce state-dependent correlation operators. Our techniques are tailored to those nuclei that can be dealt with in $LS$ coupling, which includes all nuclei up to the shell closure at $A=40$. We study mainly $p$-shell nuclei in this paper. A detailed comparison with other microscopic many-body approaches is made, using a variety of schematic nuclear interactions. It is shown that our methodology produces very good energies, and presumably also wave functions, for medium mass nuclei.
Measurements of branching fractions forB+→ρ+γ,B0→ρ0γ, andB0→ωγ
2008
We present branching fraction measurements for the radiative decays B{sup +}{yields}{rho}{sup +}{gamma}, B{sup 0}{yields}{rho}{sup 0}{gamma}, and B{sup 0}{yields}{omega}{gamma}. The analysis is based on a data sample of 465x10{sup 6} BB events collected with the BABAR detector at the PEP-II asymmetric-energy B Factory located at the Stanford Linear Accelerator Center. We find B(B{sup +}{yields}{rho}{sup +}{gamma})=(1.20{sub -0.37}{sup +0.42}{+-}0.20)x10{sup -6}, B(B{sup 0}{yields}{rho}{sup 0}{gamma})=(0.97{sub -0.22}{sup +0.24}{+-}0.06)x10{sup -6}, and a 90% C.L. upper limit B(B{sup 0}{yields}{omega}{gamma})<0.9x10{sup -6}, where the first error is statistical and the second is systematic. …
Search for the Σ⁎ state in Λc+→π+π0π−Σ+ decay by triangle singularity
2019
Abstract A Σ ⁎ resonance with spin-parity J P = 1 / 2 − and mass in the vicinity of the K ¯ N threshold has been predicted in the unitary chiral approach and inferred from the analysis of CLAS data on the γ p → K + π 0 Σ 0 reaction. In this work, based on the dominant Cabibbo favored weak decay mechanism, we perform a study of Λ c + → π + π 0 Σ ⁎ with the possible Σ ⁎ state decaying into π − Σ + through a triangle diagram. This process is initiated by Λ c + → π + K ¯ ⁎ N , then the K ¯ ⁎ decays into K ¯ π and K ¯ N produce the Σ ⁎ through a triangle loop containing K ¯ ⁎ N K ¯ which develops a triangle singularity. We show that the π − Σ + state is generated from final state interaction of …
Shape isomerism and shape coexistence effects on the Coulomb energy differences in theN=Znucleus66As and neighboringT=1multiplets
2012
Excited states of the $N=Z=33$ nucleus ${}^{66}$As have been populated in a fusion-evaporation reaction and studied using $\ensuremath{\gamma}$-ray spectroscopic techniques. Special emphasis was put into the search for candidates for the $T=1$ states. A new 3${}^{+}$ isomer has been observed with a lifetime of 1.1(3) ns. This is believed to be the predicted oblate shape isomer. The excited levels are discussed in terms of the shell model and of the complex excited Vampir approaches. Coulomb energy differences are determined from the comparison of the $T=1$ states with their analog partners. The unusual behavior of the Coulomb energy differences in the $A=70$ mass region is explained through…
Couplings in coupled channels versus wave functions: Application to theX(3872)resonance
2010
We perform an analytical study of the scattering matrix and bound states in problems with many physical coupled channels. We establish the relationship of the couplings of the states to the different channels, obtained from the residues of the scattering matrix at the poles, with the wave functions for the different channels. The couplings basically reflect the value of the wave functions around the origin in coordinate space. In the concrete case of the $X(3872)$ resonance, understood as a bound state of ${D}^{0}{\overline{D}}^{*0}$ and ${D}^{+}{D}^{*\ensuremath{-}}$ (and $c.c.$ From now on, when we refer to ${D}^{0}{\overline{D}}^{*0}$ , ${D}^{+}{D}^{*\ensuremath{-}}$, or $D{\overline{D}}…
Nuclear weak response from the combined study of beta-decay and charge-exchange reaction
2009
Studying the weak nuclear response, especially the Gamow-Teller (GT) transitions, of stable as well as unstable pf-shell nuclei, is one of the key issues in nuclear and astro-nuclear physics. We study the decay half-lives and the GT transitions starting from Tz = ±1 and ±2 mirror nuclei, respectively, by means of β decays and complementary hadronic (3 He , t) charge-exchange reactions. Under the assumption that isospin is a good quantum number, symmetry is expected for mirror nuclei and the GT transitions starting from the mirror nuclei. The half-lives and branching ratios and the measured strength distributions of GT transitions are compared and also combined for the understanding of the …
Energy and width of a narrowI=1/2DNNquasibound state
2012
The energies and widths of $DNN$ quasi-bound states with isospin I=1/2 are evaluated in two methods, the fixed center approximation to the Faddeev equation and the variational method approach to the effective one-channel Hamiltonian. The $DN$ interactions are constructed so that they dynamically generate the $\Lambda_c(2595)$ (I=0, $J^{\pi} =1/2^-$) resonance state. We find that the system is bound by about 250 MeV from the $DNN$ threshold, $\sqrt{s} \sim 3500$ MeV. Its width including both the mesonic decay and the $D$ absorption, is estimated to be about 20-40 MeV. The I=0 $DN$ pair in the $DNN$ system is found to form a cluster that is similar to the $\Lambda_c(2595)$.
Isospin dependence of electromagnetic transition strengths among an isobaric triplet
2019
*Aydın, Sezgin ( Aksaray, Yazar )