Usefulness of spin dependent electromagnetic hadronic inteference experiments

For the collision of a beam of neutral spin $\text{1}\text{2}$ particles A with a polarized target of spin $\text{1}\text{2}$charged particles B, it is shown that many spin dependent observables display a simple and characteristic structure in t which can be utilized to measure directly the magnitude and phase of the hadronic amplitudes, both helicity-flip and non flip, in the forward direction.     

Particle production in a slowly alternating electric field

The spectral density of particles produced in a slowly alternating electric field E(t) is calculated. At m²/|eE|?1 the field can be considered as constant, provided |?/E| ? m(|eE|/m²)^{$\text{3}\text{2}$}.     

Virtual effects of Higgs particles

The possibility of observing Higgs particles through virtual effects is considered in detail for a general gauge theory. The effect of charged Higgs particles on low-energy weak interaction processes, like muon decay, tau decay, nuclear beta decay, pion decay, and some higher-order processes is analyzed. The effect of flavor-changing neutral Higgs particles on rare decay modes of the muon and kaon, μe conversion, K^o-$\text{K}$^o and D^o-$\text{D}$^o mixing is also studied. We discuss constraints on possible extensions of the Weinberg-Salam model and experiments sensitive to their Higgs particles. In particular, we analyze the neutral Higgs which couple to fermions in the minimal SU(2)_L×SU(2)_R×U(1) model and find that they probably have mass greater than 100 GeV.     

On a soluble model of an antiferromagnetic chain with Dzyaloshinsky interactions. I

The one-dimensional anisotropic XY model with antisymmetric nearest-neighbour interactions (Dzyaloshinsky interactions) in the presence of a magnetic field B in the z direction is investigated. Special attention is given to the critical behaviour of the system. In the ground state, the susceptibility χ^zz has a logarithmic singularity as B → 1 provided that the strength Δ of the Dzyaloshinsky interaction obeys the inequality |Δ| ≤ |γ|, where γ is the anisotropy parameter. However, if |Δ| #62; |γ|, χ^zz diverges with a power -$\text{1}\text{2}$ singularity as B ↑ (1 + Δ² - γ²)^{$\text{1}\text{2}$}. The specific heat is studied for low temperatures. Furthermore for a few special values of γ and B the static correlation functions 〈S^α_jS^β_k〉 are evaluated in the low-temperature limit, for α, β = x, y, z and |j - k| = 1, 2. Finally we consider the chain with Dzyaloshinsky interactions only.     

Virtual mass in two-phase bubbly flow

The two-phase flow equations in their usual form are unstable. It is known that the inclusion of the virtual mass of the gas bubbles greatly improves the stability of numerical computations. Since there is some confusion concerning the proper form of the virtual-mass terms, we first present a systematic derivation of the two-fluid equations for a liquid/gas mixture from a generalised form of Hamilton's variational principle. The two-fluid theory of superfluid ⁴He has been derived in a similar way. The resulting equations do not seem to have been presented before in the literature on two-phase flow. The derivation demonstrates how the pressure of the liquid/gas mixture can be defined in a natural way. Two independent vorticities can be distinguished, each having its own law of transportation (Kelvin theorem). A subsequent stability analysis shows that at neutral stability the virtual-mass coefficient m(α) takes the form $\text{m(α)=}\text{1}\text{2}\text{α(1?α)(1?3α)}$ in the case of spherical gas bubbles with void fraction α. The corresponding local distribution of gas bubbles is anisotropic. The vanishing of the virtual mass at $\text{α=}\text{1}\text{3}$ is interpreted as the breakdown of bubbly flow. Dissipative terms are introduced and analysed in an appendix.     

On the possibility of finding light uncolored supersymmetric partners at present and future machines

Supersymmetric models allow the possibility of finding new light $\text{spin}\text{-}\text{1}\text{2}$ fermions (m <m_w, and perhaps m < 10–15 GeV, charged or neutral) that are (apart from mixing effects) the supersymmetric partners of W, Z⁰, and Higgs bosons. We provide a detailed analysis of their expected properties, production mechanisms, and signatures, with emphasis on detection at e⁺e^- colliders. Although the charged, $\text{spin}\text{-}\text{1}\text{2}$ particles resemble sequential leptons, it turns out that their properties differ enough that they might have been missed in the standard searches with normal cuts, and they still might be found with m < 18 GeV. A neutral, $\text{spin}\text{-}\text{1}\text{2}$ particle with m below about 30 GeV could exist with a clear decay signature and be singly produced at detectable rates at present machines (picobarn cross sections).     

Elastic scattering of α particles on light nuclei at Pα=7 GeV/c

Elastic scattering differential cross sections of α particles have been measured at P_α=7.0 GeV/c ($\text{T}\text{N}\text{=1.05}\text{GeV}$) on ¹H, ²H, ³He and ⁴He target up to a momentum transfer of ～4 (GeV/c)². A preliminary interpretation of the data is given in the framework of the Glauber theory.     

Specific heat and resistivity of GdSb and HoSb above the néel temperature

The specific heat C_P is found to vary as $\text{dR}\text{dT}$ in the critical region above T_N for the antiferromagnets GdSb and HoSb. This correspondence holds despite a dramatic difference between the two systems in the strength of the divergence C_P = A?^?α, $\text{? =}\text{(T ? T}{}_{\mathrm{N}}\text{)}\text{T}{}_{\mathrm{N}}$, where for HoSb we find α = 0.83 ± 0.10 while for GdSb α = 0.20 ± 0.10.     

Positron production by muon neutrinos BEBC filled with a neon-hydrogen mixture

For e⁺ energy > 0.3 GeV and 10 GeV < visible energy < 100 GeV we find that: (i) $\text{? = (v}{}_{\mathrm{\mu }}\text{+}\text{Ne}\text{→ μ}{}^{\mathrm{?}}\text{e}{}^{\mathrm{+}}\text{)/(v}{}_{\mathrm{\mu }}\text{+}\text{Ne}\text{→ μ}{}^{\mathrm{?}}\text{) = (0.41 ± 0.15)\%}$; (ii) 1.2 ± 0.5 neutral strange particles are produced per μ^?e⁺ event; (iii) the lifetime of possible positron-parent particles is < 3 × 10^?10 s (90% C.L.); (iv) the cross section for direct e⁺ production via the neutral current is < 0.2 times that via the charged current (90% C.L.); (v) the cross section for producing heavy leptons, L⁺, decaying into e⁺ … is < 0.7 × 10^?3 times that for μ^?production, implying M(L⁺) > 10 GeV.     

Periodic field-dependent photocurrent from a tungsten field emitter

We report the observation of a periodic electric-field-dependent component in the photo-current from a tungsten field emitter illuminated by the focused beam of a krypton ion laser tuned to a photon energy of ~3.51 eV. Over the field range we have investigated, the phase φ of the oscillations in the photocurrent can be related to the electric field strength F by the power law φ ∝ F^α, where $\text{α ≈ ?}\text{1}\text{2}$. In this preliminary study, we describe the frequency, amplitude, and harmonic structure of oscillations detected with the probe hole centred over the (510) region of the field emission pattern. A Fowler-Nordheim plot of the photocurrent is presented, and the nonoscillatory component is analysed on the basis of a simple theory of barrier penetration. The origin of the oscillatory component of the photocurrent is discussed.     

Massless composites with massive constituents

We construct model field theories in which a confining gauge interaction binds massive elementary fermions into massless composite particles. The massless composites are either Goldstone bosons or $\text{spin}\text{-}\text{1}\text{2}$ fermions. In these models, the manner in which exact chiral symmetries are realized changes at a critical value of the elementary fermion mass of order (e²/16π²)Λ, where Λ is the confinement scale and e is a weak gauge coupling.     

Transport properties of a Van der Waals fluid near the critical point

The behaviour of the transport coefficients of a Van der Waals fluid is studied in the one-phase region along the critical isochore of the liquid-vapour phase transition. When $\text{?=}\text{(T?T}{}_{\mathrm{c}}\text{)}\text{T}{}_{\mathrm{c}}\text{→0}$ the strongest singularity is found in the case of the bulk viscosity (??^?2). The divergence of the heat conductivity is shown to be weaker than $\text{?}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>3</mtext>}}$. The shear viscosity tends to a finite limit. The coefficients of the asymptotic laws are explicitly given. All the results are established in the region where the Ornstein-Zernike theory applies.     

The effect of a magnetic field on the heat conductivity of oxygen and oxygen - argon gas mixtures

The effects of a magnetic field on the heat conductivity of the paramagnetic O₂ and O₂-Ar gas mixtures of different compositions have been studied by using the hot-wire method. The magnetic field has been applied perpendicular to the temperature gradient so that the fractional change ($\text{Δλ}{}^{\mathrm{\perp }}\text{λ}$) of the longitudinal coefficient of thermal conductivity has been measured. For pure O₂, after applying proper corrections the experimental data obtained by using the hot-wire method agreed well with those obtained by using other methods. The experimental ($\text{Δλ}{}^{\mathrm{\perp }}\text{λ}$) data have been interpreted by applying the theory of Knaap and Beenakker and treating O₂ as a mixture of m_s = 0 and m_s = ± 1 states.For O₂-Ar mixtures, the theory of Köhler and Raum has been used and O₂ has been treated as a mixture of m_s = 0 and m_s = ±1 states. By using this approximation, the experimental ($\text{Δλ}{}^{\mathrm{\perp }}\text{λ}$) data have been interpreted fairly well and reasonable values of several cross sections have been obtained.     

Effect of magnetic field on heat flow in a polyatomic gas in intermediate pressure range

The effect of a magnetic field, B, on heat flow in a gas in an intermediate pressure range has been studied. The ratio of the heat flow changes in the fields $\text{B}\text{⊥ ?T}$ and $\text{B}\text{6 ?T}$ was found to change nonmonotonically with pressure in N₂ and CO. With the decreasing pressure, a difference is observed between the dependence of heat flow on field orientation and the corresponding angular dependence in the limiting case Kn→0 ($\text{Kn}\text{=}\text{l}\text{/L}$, $\text{l}$ is the mean free path, L is the geometric size). An expression has been obtained for the heat flow in a magnetic field for Kn ? 0.1 from the solution of an integral kinetic equation. In particular, it has been shown that the special features of the Senftleben-Beenakker effect observed with the decreasing pressure arise not only due to spherically symmetric molecule-surface interaction, but also to nonspherical scattering on walls.     

Measurements of elastic scattering in alpha-alpha and alpha-proton collisions at the CERN intersecting storage rings

We measured the elastic scattering of $\text{αα}\text{at}\text{s}\text{= 126}\text{GeV}$ and of αp at $\text{s}\text{= 89}\text{GeV}$. For αα, the differential cross section dσ/dt has a diffractive pattern minima at |t| = 0.10 and 0.38 GeV². At small |t| = 0.05?0.07 GeV², this cross section behaves like exp[(100 ± 10) t]. Extrapolating a fit to the data to the optical point, we obtained for the total cross section α_tot(αα) = 250 ± 50 mb and an integrated elastic cross section σ_e1(αα) = 45 ± mb. Another method of estimating σ_tot(αα), based on measuring the interaction rate, yielded 295 ± 40 mb. For αp, dσ/dt has aminimum at |t| = 0.20 GeV², and for 0.05 < |t| < 0.18 GeV² behaves like exp[(41 ± 2) t]. Extrapolating this slope to |t| = 0, we found σ_tot(αp) = 130 ± 20 and σ_e1(αp) = 20 ± 4mb. Results on pp elastic scattering at $\text{s}\text{= 63}\text{GeV}$ agree with previous ISR experiments.     

Fermion masses in SU(11)

Introducing several different sets of Higgs fields, possible mass spectra for the three light generations of particles in the SU(11) model of Georgi are discussed. For the u, c, t quarks there are only two possibilities: either all have masses of the same order of magnitude, or two masses are of the same order and the third is about $\text{α}{}^2\text{? 10}{}^{\mathrm{?4}}$ smaller. The corresponding masses for d,s, b quarks (and e, μ, τ leptons) are: in the first case, the masses are all same order, but a factor α or α² smaller than u, c, t. In the second case, two masses are all of the same order as the heavier top quarks, the third is smaller by a factor α. Neutrinos get small Majorana masses.     

Continuum limit of QED2 on a lattice

A path integral is defined for the vacuum expectation values of Euclidean QED₂ on a periodic lattice. Wilson's expression is used for the coupling between fermion and gauge fields. The action for the gauge field by itself is assumed to be a quadratic in place of Wilson's periodic action. The integral over the fermion field is carried out explicitly to obtain a Matthews-Salam formula for vacuum expectation values. For a combination of gauge and fermion fields $\text{G}$ on a lattice with spacing proportional to N^?1, N?Z⁺, the Matthews-Salam formula for the vacuum expectation 〈G〉_N has the form ($\text{G}$)_N=∫d_nu;W_N($\text{G}$,f), where dμ is an N-independent measure on a random electromagnetic field ? and $\text{W}{}_{\mathrm{N}}\text{(G, ?)}$ is an N-dependent function of ? determined by $\text{G}$. For a class of $\text{G}$ we prove that as N → ∞, $\text{W}{}_{\mathrm{N}}\text{(C, ?)}$ has a limit $\text{W(G, ?)}$ except possibly for a set of ? of measure zero. In subsequent articles it will be shown that ∫d_nu;W_N($\text{G}$,f) exists and lim_N→∞∫d_nu;W_N($\text{G}$,f).     

Are monojets due to unusual Z0 decays?

We examine and compare implications of several recent suggestions that events of the form $\text{p}\text{p}\text{→}\text{jet}\text{+(}\text{missing transverse momentum}\text{)}$ could be due to unusual Z⁰ decays. Two possibilities are noted: (a) $\text{Z}{}^0\text{→}\text{N}\text{N}$, where N (or $\text{N}$) is a neutral heavy lepton decaying to three neutrinos with a 10% branching ratio, and (b) Z⁰→h₁h₂, where h₁ and h₂ are two distinct spinless particles, and only the decay of h₁ is seen in the detector. Early tests of both possibilities are noted.     

Observation of a meson X→2γ, with mass 2.85 GeV/c2, produced in the charge-exchange reaction π−p → Xn at 40 GeV/c

The invariant mass spectrum of neutral final states produced in π^?p charge-exchange scattering at 40 GeV/c has been studied, searching for heavy particles decaying in 2γ. A peak is observed around 2.85 GeV/c². The cross section of the reaction π^?p→X(2.85)+n, times the branching ratio of the X→2γ decay, is measured to be $\text{σ ×}\text{BR}\text{? 2 × 10}{}^{\mathrm{?34}}\text{cm}{}^2$.     

First observation of K X-rays from pp atoms

K and L series X-rays have been observed from p$\text{p}$ atoms formed in hydrogen gas at NTP in association with annihilations into neutral particles. The total K X-ray yield is (6.5 ± 3.2) × 10^?3 per stopped antiproton. A model-dependent fit of the K X-ray spectrum gives a K_α energy of 8.9±0.3 keV, corresponding to a strong interaction shift of (?0.5±0.3) keV.