Search for elastic muon-neutrino electron scattering

One possible event of the process ν^?_μ + e^? → v^?_μ + e^? has been observed. The various background processes are discussed and the event interpreted in terms of the Weinberg theory. The 90% confidence limits on the Weinberg parameter are 0.1 < sin²θ_W < 0.6.     

Systematics of vector meson-proton scattering

The systematics of Vp scattering (V = ?, ω, φ, ψ) is studied using unitarity to relate the elastic and inelastic amplitudes. Assuming that φ and ψ are pure strange and charmed quark states, respectively, φp and ψp elastic amplitudes are shown, in the first approximation, to be generated by diffractive inelastic states. This leads to the relations B_ψ ≈ B_φ ≈ B_ω/2 ≈ B_?/2 for the elastic differential cross section slopes. The approximate m_V² is related to a similar suppression in inelastic Vp cross sections and, more speculatively, to the m_A² suppression of the hadronic production cross sections σ(pp → A).     

Pre-resonant Raman scattering in antracene crystals

The pre-resonant Raman scattering (PRRS) of anthracene crystals (T = 4.2?30 K) has been studied. A tunable dye laser (v_exc = 25000?25100 cm^-1 was used to produce an excitation close to the lowest exciton band bottom (v₀ = 25097 cm^-1). A sharp increase of the PRRS intensity when approaching the excitation light frequency v_exc to v₀ and then the not less sharp drop of the PRRS intensity close to resonance (v₀ ? v_exc ≈ 35?15 cm^-1) where observed. An extremely high PRRS sensitivity to temperature and the excitation light intensity was found. The results are explained within the framework of stimulated PRRS in anthracene crystals.     

Phase shift analysis of Kp scattering

We have analyzed data on K⁺p elastic scattering at 21 momenta covering the range 0.5–2.5 GeV/c. We present results of three phase shift analyses. One of these is an energy independent accelerated convergence expansion (ACE) analysis in which high partial waves are included through use of conformal mapping as suggested by analytic approximation theory. The other two are an energy independent and an energy smoothed conventional analysis. The ACE method gave, with the same number of parameters, a 20% average improvement in x² as well as more unique phase shift solutions. The high partial waves gave significant contributions to total and inelastic cross sections. The ACE method is also sensitive to the value of g_ΛΣ² = g_KΛN² + g_KΣN²; we have obtained the value g_ΛΣ² = 15.2 ± 2.3.     

Higher-twist effects in deep-inelastic scattering

Non-scaling, non-factorizing 1/Q² contributions to cross sections are derived for semi-inclusive deep-inelastic scattering, ?N → ?′πX. These higher twist terms are dominant at large z = p_π · p_N/Q · p_N. They provide unusual (1 ? y) terms in the cross section. as well as asymmetries in the azimuthal angle dependence. Calculations are also presented for the quark to pion fragmentation function D_π(z, Q²).     

Inverse scattering with non-overdetermined data

Let A(β,α,k) be the scattering amplitude corresponding to a real-valued potential which vanishes outside of a bounded domain D⊂R³. The unit vector α is the direction of the incident plane wave, the unit vector β is the direction of the scattered wave, k>0 is the wave number. The governing equation for the waves is [∇²+k²−q(x)]u=0 in R³. For a suitable class M of potentials it is proved that if Aq₁(−β,β,k)=Aq₂(−β,β,k),∀β∈S², ∀k∈(k₀,k₁), and q₁, q₂∈M, then q₁=q₂. This is a uniqueness theorem for the solution to the inverse scattering problem with backscattering data. It is also proved for this class of potentials that if , ∀k∈(k₀,k₁), and q₁, q₂∈M, then q₁=q₂. Here is an arbitrarily small open subset of S², and |k₀−k₁|>0 is arbitrarily small.     

Inclusive measurement of diffractive deep-inelastic ep scattering

A measurement is made of the cross section for the process ep → eXY in deep-inelastic scattering with the H1 detector at HERA. The cross section is presented in terms of a differential structure function F ₂ ^D(3) (x _P, β,Q ²) of the proton over the kinematic range 4.5 < Q ² < 75 GeV². The dependence of F ₂ ^D(3) on x _P is found to vary with β, demonstrating that a factorisation of F ₂ ^D(3) with a single diffractive flux independent of β and Q ² is not tenable. An interpretation in which a leading diffractive exchange and a subleading reggeon contribute to F ₂ ^D(3) reproduces well the x _P dependence of F ₂ ^D(3) with values for the pomeron and subleading reggeon intercepts of α_P (0) = 1.203±0.020(stat.)±0.013(sys.) _-0.035 ^+0.030 (model) and α _R (0) = 0.50 ± 0.11(stat.) ± 0.11(sys.) _-0.10 ^+0.09 (model), respectively. A fit is performed of the data using a QCD motivated model, in which parton distributions are assigned to the leading and subleading exchanges. In this model, the majority of the momentum of the pomeron must be carried by gluons in order for the data to be well described.     

Weinberg angle in the neutrino-electron scattering

According to my recent analysis, in which the use ofM _z has been found to give a more precise sin² θ _w than the use ofG _F inv _μ e→v _μ e scattering, I make calculations of sin² θ w in this process withM _z input including the full one-loop and all the leading log corrections. The result from the present data of cross-section σ(v _μ e) = (1.55±0.20)x10^?42 E _v andZ boson massM _z =92.6±1.7 GeV is sin² θ _w =0.228±0.016, which is in good agreement with the value 0.227±0.014 derived through the usual method from the data of \(v_\mu ,\bar v_\mu e\) and \(v_e ,\bar v_e e\) scatterings, and quite consistent with the world-average sin² θ w=0.228±0.004.     

Raman scattering from β-GaS

The energies and symmetries of the six first order Raman active phonon modes of the layer semiconductor β-GaS (D⁴_6h are: 22.0(E_2g), 74.2(E_1g), 188.0(A_1g), 291.4(E_1g), 295.2(E_2g) and 359.9(A_1g) cm^?1. Several additional weak Raman modes are observed with energies closely corresponding to the phonon modes found in optical absorption. These transitions involve mostly band edge phonons and can become allowed by a slight disordering of the structure or from the presence of impurities or stoichiometric defects. The disordering appears to explain the observation of optical second harmonic generation from these crystals which are predominantly centrosymmetric.     

Four-wave mixing and hyper-Raman scattering in CuCl

Non-degenerate four-wave mixing using two non-collinear laser beams with frequencies (wavevectors) ω_p, ω_t (k_p, k_t) respectively is studied in CuCl. Two emission lines at frequencies ω⁽¹⁾=2ω_t-ω_p, and ω⁽²⁾=2ω_p-ω_t are observed. Their excitation spectrum is sharply peaked if the phase-match condition k⁽¹⁾=2k_t-k_p is fulfilled. This is the case, if ω_p coincides with the hyper-Raman lines (R⁺_T, R^-_T) of the laser labelled (t) in a well-defined geometrical configuration.     

Raman scattering in monodomain RbCoF3

Polarized Raman spectra are reported for scattering from a single oriented antiferromagnetic domain in RbCoF₃. Monodomain samples were achieved by the application of a small [100] uniaxial stress. Spectra were recorded at 2 K using non-absorbed, orange laser light. The D_4h symmetry assignments for the principal features are: 34(Γ⁺₅), 335 (Γ⁺₁ and Γ⁺₁), 420 (Γ⁺₁), 950 (Γ⁺₃) and 1050 cm^-1 (Γ⁺₁). These results are not consistent with the prediction of previous models for magnetic exciton scattering.     

On low energy pion-pion scattering

Pion-pions andp-wave amplitudes are investigated by means of dispersion relations for the inverse partial wave amplitudes. Possible low energy zeros of thes-waves are taken into account and their positions as well as other parameters are determined by the imposition of the Balachandran-Nuyts crossing constraints and Martin's conditions and by postulating the existence of the ? meson. Very narrow bands of solutions are obtained, where theI=J=0 phase shifts reach 90° and thes-wave scattering lengthsa ₀ vary between 0.13 and 0.23m _π ^-1 and the ratiosa ₀/a ₂ between —1.8 and —3.5. It is shown that inelasticity or the passage through 180° of δ ₀ ⁰ near 1 GeV do not change much the predictions in the low energy region.     

Dispersion relations and low-energy elastic scattering of charged particles from nuclei: (II). Application to N-4He scattering

A “Coulomb-modified” dispersion relation is applied to low-energy p-⁴He forward elastic scattering. To check the validity of the modification, the results are compared with those deduced from n-⁴He elastic scattering. Completely analogous information is obtained for the two processes. The exchange of three bound nucleons is found to contribute strongly to N-⁴He forward scattering. The corresponding ⁴He-³H-p and ⁴He-³He-n coupling constants are evaluated as R_p = 3.8±0.3 and R_n = 3.0±0.3, respectively. These constants are related to the strength of the asymptotic wave function of nucleons in ⁴He and thus to the tail of the nucleon distribution. A comparison of R_p with the empirical proton distribution in ⁴He as deduced from e-⁴He elastic scattering shows excellent agreement. From R_p and R_n the effective ranges of the singlet ³H-p and ³He-n interactions in the ground state of ⁴He are determined to be equal, in accordance with charge symmetry, and to have a value of r_eff = 1.072±0.006 fm.     

Determination of proton-deuteron scattering lengths

An energy dependent phase-shift analysis of p+d elastic scattering below the deuteron breakup threshold has been conducted. The analysis indicates the existence of a singularity in the doublet S-wave effective range function, resulting in a very small value for the scattering length ²a_pd. The inferred value of the quartet S-wave scattering length ⁴a_pd is in good agreement with theoretical predictions.     

Polarized bhabha scattering in multiboson electroweak gauge models

The general expression for the differential cross section of the reactione ⁺ e ^?→γ,Z ₁ ⁰ ,Z ₂ ⁰ , ..., →e ⁺ e ^? with an arbitrary initial polarization state is derived in the context of electroweak gauge models with more than one neutral boson. Angular distributions, azimuthal asymmetries in the case of natural polarization, and longitudinal polarization asymmetries for models of the typeSU(2)×U(1)×G (G=?(1),S?(2)) and left-right symmetric models are compared with the standard model results. For the angular distributions withe ^± having equal helicities a～10% deviation from the standard model is predicted already below 50 GeV for models of the first type withZ ₁ ⁰ masses up to 80 GeV. At energies around the firstZ ₁ ⁰ a study of azimuthal and polarization asymmetries yields the possibility of distinguishing between different models.     

High energy muon-nucleon inelastic scattering at lowq 2

The inelastic interactions of 150 GeV positive muons produced at Fermi Laboratory have been studied in nuclear emulsion. Secondary particles produced in these interactions have been identified, the energy spectra and angular distributions for pions and protons are given. The inclusive pionproduction reaction is studied and the relative shape ofp _t ² distribution is discussed. The average charged multiplicity relations are determined as a function of different parameters and are compared with the multiplicities produced in pure hadronic interactions. The integral cross sections have been measured and are compared with the first and second powers of 1/(1+q ²/m _p ² ) forσ _exp(q ²,v), the quantity commonly called the “virtualphoton-nucleon total cross section”. The values of the structure function νW ₂ are calculated for 0.02≤q ²≤0.5. The present data are compared with other muon data at the same energy.     

Experimental results on neutrino-electron scattering

A determination of sin² θ _w based on measurements of elastic scattering of muon-neutrinos and muon-anti-neutrinos on atomic electrons is described. These purely leptonic processes were studied using the CHARM calorimeter exposed to neutrino and antineutrino wide-band beams at the CERN super proton synchrotron. A total of 83±16 neutrino-electron and 112±21 antineutrino-electron events have been detected. From the measurement of the ratio of muon-neutrino and muon-antineutrino cross-sections a value of sin² θ _w =0.211±0.037 was obtained.     

Double parton scattering contribution toW+jets

We investigate the double parton scattering production ofW ^±+jets in proton colliders. At high energies an observable signal is expected from double parton collisions when events with small transverse momentumW together with two jets balancing inp _T are selected. Double parton scattering is also a potentially serious background to several rare processes whose signal is aW ⁺+W ^?(→ev+jets) final state. A simplep _T ^W cut seems to be sufficient to separate the genuineW-pair events from the double scattering background.     

Brillouin scattering in crystals of γ-oxygen

Brillouin scattering experiments have been performed on a series of 12 independently grown crystals of γ-oxygen. The hypersonic velocities, near the triple point, are almost independent of crystal orientation. Preliminary values of the adiabatic elastic constants at the triple point are c₁₁ = 2.57, c₁₂ = 2.01, and c₄₄ = 0.28 (in units of 10¹⁰ dyn cm^?2).