Search results for "Particle physic"

ɛ-type contribution to baryon asymmetry from colored Higgs triplets

1991

In scenarios where the cosmological baryon asymmetry is generated in the decay of heavy colored Higgs triplets at the one-loop level (at least two triplets are needed), it is shown that in addition to the conventional triangle loop ({epsilon}{prime}-type effect), a new kind of diagram must be considered. This new type of diagram has its origin in the mixing of the two Higgs fields ({epsilon}-type effect). The mixing of the two Higgs fields violates {ital CP} provided they have at least two common decay channels. For small mixing angles, the new contribution can be bigger than the conventional one.

Pion photo- and electro-production and the chiral MAID interface

2016

We discuss the extended on-mass-shell scheme for manifestly Lorentz-invariant baryon chiral perturbation theory. We present a calculation of pion photo- and electroproduction up to and including order q 4 . The low-energy constants have been fixed by fitting experimental data in all available reaction channels. Our results can be accessed via a web interface, the so-called chiral MAID (http://www.kph.uni-mainz.de/MAID/chiralmaid/). We explain how our program works and how it can be used for further analysis.

Hidden-charm pentaquark state inΛb0→J/ψpπ−decay

2016

We study here the ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}p{\ensuremath{\pi}}^{\ensuremath{-}}$ reaction in analogy to the ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}p{K}^{\ensuremath{-}}$ one, and we note that in both decays there is a sharp structure (dip or peak) in the $J/\ensuremath{\psi}p$ mass distribution around 4450 MeV, which is associated in the ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}p{K}^{\ensuremath{-}}$ experiment to an exotic pentaquark baryonic state, although in ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}p{\en…

Measurement ofj/?-decays into channels containing charged and neutral antinucleons

1981

Using the nonmagnetic BONANZA detector for the detection of antineutrons and antiprotons, we measured branching ratios of theJ/ψ into baryonic final states. Our measurements give the new results:\(BR\left( {{J \mathord{\left/ {\vphantom {J {\psi \to \overline {\Sigma ^ - } }}} \right. \kern-\nulldelimiterspace} {\psi \to \overline {\Sigma ^ - } }}\Sigma ^ - } \right) = \left( {0.24 \pm 0.26} \right)\% ;BR\left( {{J \mathord{\left/ {\vphantom {J {\psi \to }}} \right. \kern-\nulldelimiterspace} {\psi \to }}\bar nn\pi ^ + \pi ^ - } \right) = \left( {0.38 \pm 0.36} \right)\% \) and an independent test for the data of the magnetic detectors.

Neutrino mass and baryon-number nonconservation in superstring models

1986

We propose new mechanisms for understanding neutrino masses in superstring models that contain ${\mathrm{E}}_{6}$-singlet zero-mass fields after compactification. We show that the low-energy gauge group of these models can be phenomenologically acceptable. We then comment on \ensuremath{\Delta}B=1 and \ensuremath{\Delta}B=2 baryon-number-violating processes in these models.

Λb and Λc baryon decays at finite values of heavy quark masses

2000

Semileptonic decays of Lambda_b and Lambda_c baryons are studied within the Relativistic Three-Quark Model using finite heavy quark mass values. Employing the same parameters as have been used previously for the description of exclusive decays of heavy baryons in the heavy quark limit we calculate the six form factors of the process and the corresponding decay rates. Our calculation shows that the ``finite mass'' corrections are important in heavy-to-light transitions and are not negligible in heavy-to-heavy transitions.

Including theΔ(1232)resonance in baryon chiral perturbation theory

2005

Baryon chiral perturbation theory with explicit $\ensuremath{\Delta}(1232)$ degrees of freedom is considered. The most general interactions of pions, nucleons, and \ensuremath{\Delta} consistent with all underlying symmetries as well as with the constraint structure of higher-spin fields are constructed. By use of the extended on-mass-shell renormalization scheme, a manifestly Lorentz-invariant effective-field theory with a systematic power counting is obtained. As applications, we discuss the mass of the nucleon, the pion-nucleon \ensuremath{\sigma} term, and the pole of the \ensuremath{\Delta} propagator.

$b\to c$ semileptonic decay of triply heavy baryons and $c\to s,d$ semileptonic decays of ground-state $cb$ baryons

2013

Fits of the baryon magnetic moments to the quark model and spectrum-generating SU(3)

1982

We show that for theoretical as well as phenomenological reasons the baryon magnetic moments that fulfill simple group transformation properties should be taken in intrinsic rather than nuclear magnetons. A fit of the recent experimental data to the reduced matrix elements of the usual octet electromagnetic current is still not good, and in order to obtain acceptable agreement, one has to add correction terms to the octet current. We have texted two kinds of corrections: U-spin-scalar terms, which are singles out by the model-independent algebraic properties of the hadron electromagnetic current, and octet U-spin vectors, which could come from quark-mass breaking in a nonrelativistic quark …

Precision measurement of the B-s(0)-(B)over-bar(s)(0) oscillation frequency with the decay B-s(0) -> D-s(-)pi(+)

2013

A key ingredient to searches for physics beyond the Standard Model in $B^{0}_{s}$ mixing phenomena is the measurement of the $B^{0}_{s}$-$\bar{B}^{0}_{s}$ oscillation frequency, which is equivalent to the mass difference $\Delta m_{s}$ of the $B^{0}_{s}$ mass eigenstates. Using the world's largest $B^{0}_{s}$ meson sample accumulated in a dataset, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected by the LHCb experiment at the CERN LHC in 2011, a measurement of $\Delta m_{s}$ is presented. A total of about 34,000 $B^{0}_{s}\rightarrow D^{-}_{s}\pi^{+}$ signal decays are reconstructed, with an average decay time resolution of 44 fs. The oscillation frequency is measured to…