Search results for "intermediate"

Evidence for the Rare DecayB→K*ℓ+ℓ−and Measurement of theB→Kℓ+ℓ−Branching Fraction

2003

We present evidence for the flavor-changing neutral current decay B-->K-*.(+).(-) and a measurement of the branching fraction for the related process B-->K.(+).(-), where .(+).(-) is either an e(+)e(-) or a mu(+)mu(-) pair. These decays are highly suppressed in the standard model, and they are sensitive to contributions from new particles in the intermediate state. The data sample comprises 123x10(6) Y(4S)-->B (B) over bar decays collected with the BABAR detector at the SLAC PEP-II e(+)e(-) storage ring. Averaging over K-(*) isospin and lepton flavor, we obtain the branching fractions B(B-->Kl(+)l(-))=(0.65(-0.13)(+0.14)+/-0.04)x10(-6) and B(B-->K(*)l(+)l(-))=(0.88(-0.29)(+0.33)+/-0.10)x10(…

Simultaneous description of the e+e−→J/ψππ(KK¯) processes

2020

In this work, we provide a simultaneous and accurate description of the ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ and ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}J/\ensuremath{\psi}$ invariant mass distributions of the recent BESIII data on ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, together with the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}J/\ensuremath{\psi}{K}^{+}{K}^{\ensuremath{-}}$ cross sections at ${e}^{+}{e}^{\ensuremath{-}}$ center-of-mass energies $q=4.23\text{ }\text{ }\mathrm{GeV}$ and $q=4.26\text{ }\text{ }\mathrm{GeV}$. The rescattering effects between p…

Electroweak effects in intermediate energy physics

2008

Triangle mechanisms in the build up and decay of the N*(1875)

2017

We have studied the $N^*(1875) (3/2^-)$ resonance with a multichannel unitary scheme, considering the $\Delta \pi$ and $\Sigma^* K$, with their interaction extracted from chiral Lagrangians, and then have added two more channels, the $N^*(1535) \pi$ and $N \sigma$, which proceed via triangle diagrams involving the $\Sigma^* K$ and $\Delta \pi$ respectively in the intermediate states. The triangle diagram in the $N^*(1535) \pi$ case develops a singularity at the same energy as the resonance mass. We determine the couplings of the resonance to the different channels and the partial decay widths. We find a very large decay width to $\Sigma^* K$, and also see that, due to interference with othe…

On the merit of a Central Limit Theorem-based approximation in statistical physics

2012

The applicability conditions of a recently reported Central Limit Theorem-based approximation method in statistical physics are investigated and rigorously determined. The failure of this method at low and intermediate temperature is proved as well as its inadequacy to disclose quantum criticalities at fixed temperatures. Its high temperature predictions are in addition shown to coincide with those stemming from straightforward appropriate expansions up to (k_B T)^(-2). Our results are clearly illustrated by comparing the exact and approximate temperature dependence of the free energy of some exemplary physical systems.

The Bc → J/ΨKD weak decay and its relation with the D*s0(2317) resonance

2016

We study the influence of the D * s 0 (2317) + resonance in the decay B c → J/ψKD . In this process, we consider that the B c meson decays first into J/ψ and the quark pair cs , and then the quark pair hadronizes into DK or D s η components. The final state interaction, generating the D * s 0 (2317) + resonance, is described by the chiral heavy meson unitary approach. With the parameters chosen in order to match the pole position of the D * s 0 (2317) + , we obtain the DK invariant mass distribution of the decay B c → J/ψDK , and also the rate for B c → J/ψD * s 0 (2317). We predict the ratio of these two magnitudes. This decay mechanism has not been measured yet, and it would provide insig…

Scalar ΛN and ΛΛ interactions within a chiral unitary approach

2008

We study the central part of the ΛN potential by considering the correlated and uncorrelated two-meson exchange besides the ω exchange contribution. The correlated two-meson is evaluated in a chiral unitary approach. We find that a short range repulsion is generated by the correlated two-meson potential which also produces an attraction in the intermediate distance region. The uncorrelated two-meson exchange produces a sizable attraction in all cases which is counterbalanced by ω exchange contribution.

Two-photon exchange contribution to elastic e− -proton scattering: Full dispersive treatment of πN states and comparison with data

2017

We evaluate the two-photon exchange correction to the elastic electron-proton scattering cross section within a dispersive framework. Besides the elastic contribution, we account for all $\ensuremath{\pi}N$ intermediate state contributions using the phenomenological MAID fit as an input. We develop a novel method for the analytical continuation of the two-photon exchange amplitudes into the unphysical region and generalize our previous work to the momentum transfer region $0.064\text{ }\text{ }{\mathrm{GeV}}^{2}\ensuremath{\lesssim}{Q}^{2}\ensuremath{\lesssim}1\text{ }\text{ }{\mathrm{GeV}}^{2}$. We compare our results with recent OLYMPUS, CLAS and VEPP-3 data as well as with empirical fits…

AC Stark shift of the ground state of atomic hydrogen

2004

An analytical expression for the second-order AC Stark shift of the ground state of atomic hydrogen is derived, which is convergent for negative as well as for positive energies of intermediate states except for the resonances. To clarify the applicability of the second-order perturbation theory, we compared results with those which are obtained by us and other authors using nonperturbative methods. It appears that values obtained for the AC Stark shift using our simple formula agree on average with Floquet-method calculations up to the field strength F=0.12 (a.u.), which corresponds to I=1015 W/cm2.

Shock waves and QPOs in 2D rotating accretion flows around black holes

2008

We examine numerically shock waves formed in 2D rotating accretion flows around a stellar‐mass and a supermassive black holes, while taking account of the cooling and heating of the gas and the radiation transport. As the results, we obtain general properties of the shock oscillations and the luminosity behaviors as QPOs independent of the black hole masses.