The equivalent photon approximation for coherent processes at colliders

We consider coherent electromagnetic processes for colliders with short bunches, in particular the coherent bremsstrahlung (CBS). CBS is the radiation of one bunch particles in the collective field of the oncoming bunch. It can be a potential tool for optimizing collisions and for measuring beam parameters. A new simple and transparent method to calculate CBS is presented based on the equivalent photon approximation for this collective field. The results are applied to the??-factoryDA??NE. For this collider about 5·10¹⁴ d E _??/E _?? photons per second are expected in the photon energyE _?? range from the visible light up to 25 eV.     

Comments on the phenomenology of two current models for the�� �� 3�� v �� decay

A comparison of the phenomenology of two current????3?? v _?? decay models is presented. These are the Kühn and Santamaria model and the Isgur et al. model. Features in which the two models differ are identified and the effects of those features on the shape of the invariant 3?? mass squared distribution and the?? ₁ resonance model parameters are examined. It is found that the parametrization of the strong form factors is the feature which most influences the distribution shape and the resonance parameters.     

Improving the empirical model for plasma nitrided AISI 316L corrosion resistance based on M?ssbauer spectroscopy

Traditional plasma nitriding treatments using temperatures ranging from approximately 650 to 730 K can improve wear, corrosion resistance and surface hardness on stainless steels. The nitrided layer consists of some iron nitrides: the cubic ?? ^?? phase (Fe₄N), the hexagonal phase ?? (Fe_2???3N) and a nitrogen supersatured solid phase ?? _N . An empirical model is proposed to explain the corrosion resistance of AISI 316L and ASTM F138 nitrided samples based on Mössbauer Spectroscopy results: the larger the ratio between ?? and ?? ^?? phase fractions of the sample, the better its resistance corrosion is. In this work, this model is examined using some new results of AISI 316L samples, nitrided under the same previous conditions of gas composition and temperature, but at different pressure, for 3, 4 and 5 h. The sample nitrided for 4 h, whose value for ??/?? ^?? is maximum (=?0.73), shows a slightly better response than the other two samples, nitrided for 5 and 3 h (??/?? ^?? = 0.72 and 0.59, respectively). Moreover, these samples show very similar behavior. Therefore, this set of samples was not suitable to test the empirical model. However, the comparison between the present results of potentiodynamic polarization curves and those obtained previously at 4 and 4.5 torr, could indicated that the corrosion resistance of the sample which only presents the ?? _N phase was the worst of them. Moreover, the empirical model seems not to be ready to explain the response to corrosion and it should be improved including the ?? _N phase.     

Searching for the QCD critical point in AA collisions at CERN SPS

We investigate the transverse momentum correlations of pairs of opposite charged pions near their production threshold. Through intermittency analysis, we search for power-law dependence on observation scale, as dictated by critical QCD. We analyze the data on the most central collisions in four A systems (A = p, C, Si, Pb) at maximum SPS energy. We find a significant effect for the SiSi system approaching in size the critical QCD predictions as measured by the intermittency index ? ₂. Absence of this effect in the (?? ^?, ?? ^?) sector of the SiSi system gives further support that the observed behavior in the isoscalar mode is of critical origin.     

Exchange,production and decay of the Z meson (JPC = 2−−)

Recent high-statistics data for π^?p→ω⁰n indicate the presence of an amplitude with exchange quantum numbers in the series J^PC = 2^?? 4^??,… Previous phenomenological and theoretical estimates of reggeised Z exchange J^PC = 2^??) are shown to be in good agreement with data. Implications for observing the exchange of its EXD partner (the much sought A₁) and other unnatural parity states are discussed with reference to a with a quark model estimate of its branching ratio, we predict the cross section for production of the Z and its subsequent decay into ωπ. The prospects for a partial-wave analysis of the ωπ enhancement observed at 1700 MeV are discussed.     

Mechanism of pion production in αp scattering at 1 GeV/nucleon

An analysis of the experimental data on one-pion and two-pion production in the p(??, ????)X reaction studied in a semi-exclusive experiment at an energy of E _?? = 4.2 GeV has been performed. The obtained results demonstrate that the inelastic ??-particle scattering on the proton at the energy of the experiment proceeds either through excitation and decay of the ?? resonance in the projectile ?? particle, or through excitation in the target proton of the Roper resonance, which decays into a nucleon and a pion, or a nucleon and a ?? meson??a system of two pions in the isospin I = 0, S-wave state.     

Beam energy dependence of azimuthal anisotropy at RHIC-PHENIX

Recent PHENIX measurements of the elliptic (?? ₂) and hexadecapole (?? ₄) Fourier flow coefficients for charged hadrons as a function of transverse momentum (p _T ), collision centrality and particle species are presented and compared with results from the PHOBOS and STAR Collaborations respectively. The status of extensions to future PHENIX measurements at lower beam energies is also discussed.     

Futurev �� oscillation experiments and present data

Our goal in this paper is to examine the discovery covery potential of laboratory experiments searching for the oscillationv _??(?? _e)??v _??, in the light of recent data on solar and atmospheric neutrino experiments, which we analyse together with the most restrictive results from laboratory experiments on neutrino oscillations. In order to explain simultaneouslyall present results we use a four-neutrino framework, with an additional sterile neutrino. Our predictions are rather pessimistic for the upcoming experiments NOMAD and CHORUS, which, we find, are able to explore only a small area of the oscillation parameter space. On the other hand, the discovery potential of future experiments is much larger. We consider three examples. E803, which is approved to operate in the future Fermilab main injector beam line, MINOS, a proposed long-baseline experiment also using the Fermilab beam, and NAUSICAA, an improved detector which improves by an order of magnitude the performance of CHORUS/NOMAD and can be operated either at CERN or at Fermilab beams. We find that those experiments can cover a very substantial fraction of the oscillation parameter space, having thus a very good chance of discoveringboth v _????v _?? and?? _e??v _?? oscillation modes.     

New physics with three-photon events at LEP

The effect a generalZ??3?? vertex in the reactione ⁺ e ^???3?? is studied with a particular attention to LEP searches. We give exact analytical expressions including realistic cuts for the signal and present a detailed analysis based on a Monte Carlo that includes the effect of the irreducible 3?? QED cross section. As special applications we discuss the effect of heavy scalars, fermions and gauge bosons.     

Neutron-rich hypernuclei in the chiral soliton model

The binding energies of neutron-rich strangeness S = ?1 hypernuclei are estimated in the chiral soliton approach using the bound state rigid oscillator version of the SU(3) quantization model. Additional binding of strange hypernuclei in comparison with nonstrange neutron-rich nuclei takes place at not large values of atomic (baryon) numbers, A = B ?? ??10. This effect becomes stronger with increasing isospin of nuclides, and for the ??nuclear variant?? of the model with rescaled Skyrme constant e. Binding energies of _?? ⁸ He and recently discovered _?? ⁶ H satisfactorily agree with data. Hypernuclei _?? ⁷ H, _?? ⁹ He are predicted to be bound stronger in comparison with their nonstrange analogues ⁷H, ⁹He; hypernuclei _?? ¹⁰ Li, _?? ¹¹ LI, _?? ¹² Be, _?? ¹³ Be, etc. are bound stronger in the nuclear variant of the model.     

Stimulated Raman scattering in natural crystals of SrSO4, BaSO4 and PbSO4: High-order Stokes and anti-Stokes generation with?single-wavelength UV, visible, and near-IR excitation, as?well?as cascaded up-conversion nonlinear �� (3)?�� (3) lasing effects under dual-wavelength picosecond collinear coherent pumping

Orthorhombic crystals of SrSO₄, BaSO₄, and PbSO₄, known as natural crystals celestine, barite, and anglesite, were found to be attractive ?? ⁽³⁾-active nonlinear optical materials. High-order Stokes and anti-Stokes picosecond generation that spans almost two octaves has been recorded with single-wavelength laser excitation in the UV, visible, and near-IR ranges. All recorded Raman induced lasing components were identified and attributed to the SRS-promoting vibration modes of the studied crystals (?? _SRS??999?cm^?1 for SrSO₄,?? _SRS??985?cm^?1 for BaSO₄ and ?? _SRS??977?cm^?1 for PbSO₄). Under dual-wavelength (?? _f1=1.06415???m + ?? _f2=0.53207???m) collinear coherent picosecond pumping several new manifestations of cascaded ?? ⁽³⁾??? ⁽³⁾ nonlinear up-conversion lasing effects were observed in BaSO₄ and SrSO₄ crystals. We classify all three studied sulfate crystals as promising SRS-active materials for Raman laser frequency converters and as efficient ?? ⁽³⁾-crystals that efficiently generate Stokes and anti-Stokes frequency combs, which can enable experiments of ultra-short pulse syntheses.     

Preparation and characterisation of isotopically enriched Ta2O5 targets for nuclear astrophysics studies

Level energies in two-quasiparticle (2qp) structures in ¹⁵⁶ ₆₁Pm₉₅ are evaluated using the phenomenological rotor-particle model for odd-odd deformed nuclei with the inclusion of the residual p-n interaction contribution. Using these results as location guides, the experimental data from a recent ¹⁵⁶Nd decay study are used to construct a level scheme for ¹⁵⁶Pm with excitation energies upto 550 keV, wherein 26 (out of 30) ????s reported in ¹⁵⁶Nd decay are incorporated. Spin-parities and configuration assignments are suggested for 15 levels, in addition to the two isomers, in this energy domain. These investigations point to the need for information on higher-energy ????s and on ??-?? and ??-?? coincidence data from ¹⁵⁶Nd ??-decay to confirm these assignments.     

Efficient passively Q-switched Nd:YLF TEM00-mode laser at 1053 nm: selection of polarization with birefringence

The natural birefringence of the Nd:YLF crystal is utilized to achieve a reliable TEM₀₀-mode linearly polarized laser at 1053 nm in a compact concave-plano resonator. The efficient selection of the polarization relies on the combined effect of the difference in diffraction angle for ??- and ??-polarization of a wedged laser crystal and the alignment sensitivity of an optical resonator. We further employ a Cr⁴⁺:YAG saturable absorber to perform the passively Q-switched operation. At an incident pump power of 12?W, the maximum average output power is up to 2.3?W with a pulse repetition rate of 8?kHz and a pulse width of 9?ns. The pulse energy and peak power are found to be 288???J and 32?kW, respectively.     

Glauber Dynamics for the Mean-Field Potts Model

We study Glauber dynamics for the mean-field (Curie-Weiss) Potts model with q??3 states and show that it undergoes a critical slowdown at an inverse-temperature ?? _s (q) strictly lower than the critical ?? _c (q) for uniqueness of the thermodynamic limit. The dynamical critical ?? _s (q) is the spinodal point marking the onset of metastability. We prove that when ??<?? _s (q) the mixing time is asymptotically C(??,q)nlogn and the dynamics exhibits the cutoff phenomena, a sharp transition in mixing, with a window of order n. At ??=?? _s (q) the dynamics no longer exhibits cutoff and its mixing obeys a power-law of order n ^4/3. For ??>?? _s (q) the mixing time is exponentially large in n. Furthermore, as ?????? _s with n, the mixing time interpolates smoothly from subcritical to critical behavior, with the latter reached at a scaling window of O(n ^?2/3) around ?? _s . These results form the first complete analysis of mixing around the critical dynamical temperature??including the critical power law??for a model with a first order phase transition.     

Studies on frequency and gate voltage effects on the dielectric properties of Au/n-Si (110) structure with PVA–nickel acetate composite film interfacial layer

The admittance technique was used in order to investigate the frequency dependence of dielectric constant (????), dielectric loss (????), dielectric loss tangent (tan??), the ac electrical conductivity (?? _ac), and the electric modulus of PVA (Ni-doped) structure. Experimental results revealed that the values of ???? , ????, (tan??), ?? _ac and the electric modulus show fairly large frequency and gate bias dispersion due to the interface charges and polarization. The ?? _ac is found to increase with both increasing frequency and voltage. It can be concluded that the interface charges and interfacial polarization have strong influence on the dielectric properties of metal?Cpolymer?Csemiconductor (MIS) structures especially at low frequencies and in depletion and accumulation regions. The results of this study indicate that the ???? values of Au/PVA/n-Si with Nickel-doped PVA interfacial layer are quite higher compared to those with pure and other dopant/mixture??s of PVA.     

Nucleation rate of the quark-gluon plasma droplet at finite quark chemical potential

The nucleation rate of quark-gluon plasma (QGP) droplet is computed at finite quark chemical potential. In the course of computing the nucleation rate, the finite size effects of the QGP droplet are taken into account. We consider the phenomenological flow parameter of quarks and gluons, which is dependent on quark chemical potential and we calculate the nucleation rate of the QGP droplet with this parameter. While calculating the nucleation rate, we find that for low values of quark phenomenological parameter ?? _q , nucleation rate is negligible and when ?? _q increases, nucleation rate increases significantly.     

High power cryogenic targets

Radiative corrections to parity violating deep inelastic electron scattering (PVDIS) are reviewed including a discussion of the renormalization group evolution (RGE) of the weak mixing angle. Recently obtained results on hypothetical Z?? bosons??for which parity violating observables play an important rôle??are also presented.     

Constraints on large-extra-dimensions model through 125 GeV Higgs pair production at the LHC

Based on the analysis of 5?fb^?1 of data at the LHC, the ATLAS and CMS collaborations have presented evidence for a Higgs boson with a mass in the 125 GeV range. We consider the 125 GeV neutral Higgs pair production process in the context of large-extra-dimensions (LED) model including the Kaluza?CKlein (KK) excited gravitons at the LHC. We consider the standard model (SM) Higgs pair production in gluon?Cgluon fusion channel and pure LED effects through graviton exchange as well as their interferences. It is shown that such interferences should be included; the LED model raises the transverse momentum (P _t ) and invariant mass (M _HH ) distributions at high scales of P _t and M _HH of the Higgs pair production. By using the Higgs pair production we could set the discovery limit on the cutoff scale M _S up to 6 TeV for ??=2 and 4.5 TeV for ??=6.     

Three-Frequency Composite Multipulse Nuclear Quadrupole Resonance Technique for Explosive Detection

New method of multifrequency nuclear quadrupole resonance (NQR) for the explosive detection has been proposed. This technique consists of application of the series of composite excitation circles, each consisting of two or three successive pulses of different frequencies. In this work, we study in detail the multipulse sequence consisting of n excitation sets, each set consists of three pulses. The first pulse is applied with frequency ?? _?, the second pulse with frequency ?? ₀, and the third pulse with frequency ?? _?C, but with a shifted phase. The NQR signal is detected at the frequency ?? ₊. The maximal amplitude of the detected signal is obtained by tuning the pulse parameters at frequencies ?? _? and ?? ₀. We have shown that the phase of the NQR signal at the frequency ?? ₊ second part of the composite pulse with the frequency ?? ₀ the signals with different phases to suppress the spurious signals. The method could be used for increasing the NQR signal, avoiding the spurious signals and improving the reliability of NQR detection. Possible applications of the method for the explosive detection are also discussed.