General classical theory of spinning particles in a meson field

An exact classical theory of the motion of a point dipole in a meson field is given which takes into account the effects of the reaction of the emitted meson field. The meson field is characterized by a constant $\chi =\mu /\hslash $ of the dimensions of a reciprocal length, $\mu $ being the meson mass, and as $\chi \rightarrow $ 0 the theory of this paper goes over continuously into the theory of the preceding paper for the motion of a spinning particle in a Maxwell field. The mass of the particle and the spin angular momentum are arbitrary mechanical constants. The field contributes a small finite addition to the mass, and a negative moment of inertia about an axis perpendicular to the spin axis. A cross-section (formula (88 a)) is given for the scattering of transversely polarized neutral mesons by the rotation of the spin of the neutron or proton which should be valid up to energies of 10$^{9}$ eV. For low energies E it agrees completely with the old quantum cross-section, having a dependence on energy proportional to p$^{4}$/E$^{2}$ (p being the meson momentum). At higher energies it deviates completely from the quantum cross-section, which it supersedes by taking into account the effects of radiation reaction on the rotation of the spin. The cross-section is a maximum at E $\sim $ 3$\cdot $5$\mu $, its value at this point being 3 $\times $ 10$^{-26}$ cm.$^{2}$, after which it decreases rapidly, becoming proportional to E$^{-2}$ at high energies. Thus the quantum theory of the interaction of neutrons with mesons goes wrong for E $\gtrsim $ 3$\mu $. The scattering of longitudinally polarized mesons is due to the translational but not the rotational motion of the dipole and is at least twenty thousand times smaller. With the assumption previously made by the present author that the heavy partilesc may exist in states of any integral charge, and in particular that protons of charge 2e and - e may occur in nature, the above results can be applied to charged mesons. Thus transversely polarised mesons should undergo a very big scattering and consequent absorption at energies near 3$\cdot $5$\mu $. Hence the energy spectrum of transversely polarized mesons should fall off rapidly for energies below about 3$\mu $. Scattering plays a relatively unimportant part in the absorption of longitudinally polarized mesons, and they are therefore much more penetrating. The theory does not lead to Heisenberg explosions and multiple processes.

Including the fermion vacuum fluctuations in the (2+1) flavor Polyakov quark-meson model

We consider the (2 + 1) flavor Polyakov quark-meson model and study the effect of including fermion vacuum fluctuations on the thermodynamics and phase diagram. The resulting model predictions are compared to the recent QCD lattice simulations by the HotQCD and Wuppertal-Budapest collaborations. The variation of the thermodynamic quantities across the phase transition region becomes smoother. This results in better agreement with the lattice data. Depending on the value of the mass of the sigma meson, including the vacuum term results in either pushing the critical end point into higher values of the chemical potential or excluding the possibility of a critical end point altogether.

Fluctuations and correlations of conserved charges in the (2+1) Polyakov quark meson model

We consider the (2 + 1) flavor Polyakov quark meson model and study the fluctuations (correlations) of conserved charges up to sixth (fourth) order. A comparison is made with lattice data wherever available and overall good qualitative agreement is found, more so for the case of the normalized susceptibilities. The model predictions for the ratio of susceptibilities go to that of an ideal gas of hadrons as in hadron resonance gas model at low temperatures while at high temperature the values are close to that of an ideal gas of massless quarks. Our study provides a strong basis for the use of the Polyakov quark meson model as an effective model to understand the topology of the QCD phase diagram. DOI: 10.1103/PhysRevD.86.114021 PACS numbers: 12.39.-x, 05.40.-a, 12.38.Aw, 12.38.Mh

Measurement of the direct CP asymmetry in b-->s+gamma via sum of exclusive B Meson decays using the BABAR detector

We perform a measurement of direct CP violation in b to s+gamma Acp, and the measurement of a difference between Acp for neutral B and charged B mesons, Delta A_{X_s\gamma}, using 429 inverse femtobarn of data recorded at the Upsilon(4S) resonance with the BABAR detector. B mesons are reconstructed from 16 exclusive final states. Particle identification is done using an algorithm based on Error Correcting Output Code with an exhaustive matrix. Background rejection and best candidate selection are done using two decision tree-based classifiers. We found $\acp = 1.73%+-1.93%+-1.02% and Delta A_X_sgamma = 4.97%+-3.90%+-1.45% where the uncertainties are statistical and systematic respectively. Based on the measured value of Delta A_X_sgamma, we determine a 90% confidence interval for Im C_8g/C_7gamma, where C_7gamma and C_8g are Wilson coefficients for New Physics amplitudes, at -1.64 < Im C_8g/C_7gamma < 6.52.

Flavor SU(3) predictions for charmed baryon and B-meson decays

The predictions of the SU(3) flavor symmetry of the strong interactions for the weak decay of charmed baryons and B-mesons are detailed. It is hoped that comparison between these predictions and experiment will shed some light on the underlying dynamics involved in these weak decays. Although only a few decay modes of the charmed baryons and B-mesons have been studied experimentally it is hoped that the next generation of B-factories and even Z-decays at LEP will provide enough events to test these predictions.

I. Current commutators in quantum electrodynamics. II. Electromagnetic mass differences of the pseudoscalar meson and baryon octets

This thesis is in two parts. In the first section, the operator structure of the singular terms in the equal-time commutator of space and time components of the electromagnetic current is investigated in perturbation theory by establishing a connection with Feynman diagrams. It is made very plausible that the singular term is a c number. Some remarks are made about the same problem in the electrodynamics of a spinless particle.

In the second part, an SU(3) symmetric multi-channel calculation of the electromagnetic mass differences in the pseudoscalar meson and baryon octets is carried out with an attempt to include some of the physics of the crossed (pair annihilation) channel along the lines of the recent work by Ball and Zachariasen. The importance of the tensor meson Regge trajectories is emphasized. The agreement with experiment is poor for the isospin one mass differences, but excellent for those with isospin two.

Two topics in elementary particle physics. I. Crossing as a group and elimination of exotic channels. II. Real parts of meson-nucleon forward scattering amplitudes.

I. Crossing transformations constitute a group of permutations under which the scattering amplitude is invariant. Using Mandelstem's analyticity, we decompose the amplitude into irreducible representations of this group. The usual quantum numbers, such as isospin or SU(3), are "crossing-invariant". Thus no higher symmetry is generated by crossing itself. However, elimination of certain quantum numbers in intermediate states is not crossing-invariant, and higher symmetries have to be introduced to make it possible. The current literature on exchange degeneracy is a manifestation of this statement. To exemplify application of our analysis, we show how, starting with SU(3) invariance, one can use crossing and the absence of exotic channels to derive the quark-model picture of the tensor nonet. No detailed dynamical input is used.

II. A dispersion relation calculation of the real parts of forward π^±p and K^±p scattering amplitudes is carried out under the assumption of constant total cross sections in the Serpukhov energy range. Comparison with existing experimental results as well as predictions for future high energy experiments are presented and discussed. Electromagnetic effects are found to be too small to account for the expected difference between the π^-p and π⁺p total cross sections at higher energies.

The polarization of the recoil proton in ETA photoproduction

We measured the recoil proton polarization in the process γp → pη at the 1.5 GeV Caltech electron synchrotron, at photon energies from 0.8 to 1.1 GeV, and at center-of-mass production angles around 90°. A counter-spark chamber array was used to determine the kinematics of all particles in the final state of the partial mode γp → pη (η → 2γ). The protons' polarization was determined by measuring an asymmetry in scattering off carbon. Analysis of 280,000 pictures yielded 2400 useful scatters with a background which was 30% of the foreground. The polarization results show a sizeable opposite parity interference at 830 MeV, 950 MeV, and 1100 MeV.

π+ photoproduction at angles from 6° to 90° C.M. and energies from 589 to 1269 MeV

The differential cross section for the reaction γp → π⁺n was measured at 32 laboratory photon energies between 589 and 1269 MeV at the Caltech Synchrotron. At each energy, data have been obtained at typically fifteen π⁺ c.m. angles between 6° and 90°. A magnetic spectrometer was used to detect the π⁺ photo-produced in a liquid hydrogen target. Two Cherenkov counters were used to reject the background of positrons and protons. The data clearly show the presence of a pole in the production amplitude due to the one pion exchange. Moravcsik fits to the 32 angular distributions, including data from another experiment, are presented. The extrapolation of these fits to the pole gives a value for the pion-nucleon coupling constant of 14.5 which is consistent with the accepted value. The second and third pion-nucleon resonances are evident as peaks in the total cross section and as changes in the shape of the angular distributions. At the third resonance there is evidence for both a D5/2 and an F5/2 amplitude. The absence of large variations in the 0° and 180° cross sections implies that the second and third resonances are mostly produced from an initial state with helicity ± 3/2.

Photoproduction of charged pion pairs from hydrogen at photon energies between 800 and 1500 MeV

The reaction γ + p p + π⁺ + π^- has been studied for photon energies between 800 and 1500 MeV and for dipion masses between 510 and 900 MeV. The bremsstrahlung beam from the Caltech synchrotron was passed through a liquid hydrogen target and spark chambers were used to detect the three final particles. In addition, the proton energy was determined by a range measurement. Approximately 40,000 photographs were taken, yielding 3018 acceptable events. The results were fit to an incoherent combination of the N*(1238) resonance, the p^o (750) resonance, and three-body phase space, with various models being tried for p^o production. The total cross section for p^o production is consistent with previous experiments. However, the angular dependence of the cross section is slightly more peaked in the forward direction, and the ratio of p^o production to phase space production is larger than previously observed.

However, since this experiment was only sensitive to the production angles cos θ cm ≥ .75, statistical fluctuations and/or an anisotropic distribution of background production have a severe influence on the p^o to background ratio. Of the p^o models tested, the results prefer p^o production by the one pion exchange mechanism with a very steep form factor dependence. The values of the mass and width of the p^o found here are consistent with previous experiments.

Photoproduction of ETA mesons from hydrogen at photon energies between 0.8 and 1.45 GeV

We measured the differential cross section of the process γp → pƞ at the 1.5 GeV Caltech electron synchrotron, at photon energies from 0.8 to 1.45 GeV, at various angles between 45° and 100° in the center of mass. A counter-spark chamber array was used to determine the kinematics of all particles in the final state of the partial mode γp → pƞ (ƞ → 2γ). Analysis of 40,000 pictures yielded 6,000 events above a background which varied with energy from 5% to 30% of foreground. The cross section shows an energy dependence confirming earlier results up to 1000 MeV, but with improved statistics; it then remains roughly constant (at 50° C.M.), to 1.45 GeV. The data show a small angular variation, within the limited range covered, at energies between 1000 and 1100 MeV.

Preliminary study on the photoproduction of hydroxyl radicals in aqueous solution with Aldrich humic acid, algae and Fe(III) under high-pressure mercury lamp irradiation

Under a high-pressure mercury lamp (HPML) and using an exposure time of 4 h, the photoproduction of hydroxyl radicals ((OH)-O-.) could be induced in an aqueous solution containing humic acid (HA). Hydroxyl radicals were determined by high-performance liquid chromatography using benzene as a probe. The results showed that (OH)-O-. photoproduction increased from 1.80 to 2.74 muM by increasing the HA concentration from 10 to 40 mg L-1 at an exposure time of 4 h (pH 6.5). Hydroxyl radical photoproduction in aqueous solutions of HA containing algae was greater than that in the aqueous solutions of HA without algae. The photoproduction of (OH)-O-. in the HA solution with Fe(111) was greater than that of the solution without Fe(III) at pH ranging from 4.0 to 8.0. The photoproduction of (OH)-O-. in HA solution with algae with or without Fe(111) under a 250 W HPML was greater than that under a 125 W HPML. The photoproduction of (OH)-O-. in irradiated samples was influenced by the pH. The results showed that HPML exposure for 4 h in the 4-8 pH range led to the highest (OH)-O-. photoproduction at pH 4.0.