Statistical fluctuations and the double differential cross section for energy and angle in deep inelastic reactions

We use a model which accounts for dissipation and statistical fluctuations to compute the double differential cross sectiond ²σ/dθdE. The calculation is performed for the 388 MeV Ar + Th system. The typical experimental pattern of the cross section versus angle and energy is reproduced.     

Precise measuring mass and spin of dark matter particles at ILC via singularities in the single lepton energy spectrum

We consider models, in which stability of Dark Matter particles D is ensured by the conservation of the new quantum number, called D-parity here. Our models contain also charged D-odd particle D ^±. We propose method for precision measuring masses and spin of D-particles via the study of energy distribution of single lepton (e or μ) in the process e ⁺ e ^? → D ⁺ D ^? → DDW ⁺ W ^? with the observable state dijet + μ (or e) + nothing. It is shown that this distribution has kinematically determined singular points (upper edge and kinks or peak). Measuring of their positions allow to determine precisely masses of D and D ^±. After this, even a rough measuring of corresponding cross section allows to determine the spin of D particles.     

Measurement of elastic J/ψ photoproduction at HERA

The reaction γ p → J/ψ p has been studied in ep interactions using the ZEUS detector at HERA. The cross section for elastic J/ψ photoproduction has been measured as a function of the photon-proton centre of mass energy W in the range 40 < W < 140 GeV at a median photon virtuality Q ² of 5 × 10^?5 GeV². The photoproduction cross section, σ_{γp→ J/ψp}, is observed to rise steeply with W. A fit to the data presented in this paper to determine the parameter δ in the form σ_{γp→ J/ψp} α W ^δ yields the value δ = 0.92±0.14±0.10. The differential cross section dσ/d ¦t¦is presented over the range ¦t¦< 1.0 GeV² where t is the square of the four-momentum exchanged at the proton vertex. dσ/d ¦t¦falls exponentially with a slope parameter of $4.6pm 0.4_{-0.6}^{+0.4} {? GeV}^{-2}$. The measured decay angular distributions are consistent with s-channel helicity conservation.     

Study of Strangeness Photoproduction on the Neutron in the Threshold Region

Photoproduction of the neutral kaon on the deuteron has been investigated at the Research Center for Electron Photon Science, Tohoku University. We constructed the Neutral Kaon Spectrometer-2 for the detection of charged particles from the decay of the neutral kaon and the hyperon. We obtained a momentum distribution of K ⁰ with the inclusive measurement. It was consistent with the previous measurement. The total cross section of γ + d → K ⁰ + Λ + p was estimated from the measured integral cross section of γ + d → Λ + X. The total cross section with respect to the photon energy was compared with the theoretical calculations. It favored the Saclay-Lyon A model calculation with the ratio of the neutral to charged coupling constants of the axial-vector meson, K ₁, as ~ ?1.5. The energy dependence and the magnitude of the total cross section were similar to the total cross section of γ + p → K ⁺ Λ.     

Production and decay of W boson in electron-positron annihilation

We study the characteristics of the μe events due to e⁺e^? → W⁺W^? and the subsequent leptonic decay of W^±, in the Weinberg-Salam model. The differential cross section for W production is given for non-polarized electron-positron beams as well as transversely polarized beams. The energy angle distributions as well as angular correlations of the final μe events are presented for beam energy of 100 + 100 GeV. Potential backgrounds are also discussed.     

Inelastic electron-deuteron scattering with final-state interactions

Measurements of the cross sectiond ² σ/dΩ dE′ for the inelastic electron-deuteron scattering processe+d→e+n+p have been used to determine the electromagnetic structure of the neutron. The effects on the theoretical cross section of the structure of the deuteron and of interactions between the outgoing nucleons are examined in detail. We start with the relativistic invariant expressions of the one-nucleon exchange diagram including deuteron structure to obtain the interaction Hamiltonian. For the disintegration near the quasi-elastic peak thed-n-p vertex function can be represented by nonrelativistic deuteron wave functions. The final state interaction is calculated from phenomenological nucleon-nucleon potentials. The rescattering corrections are found to lead to a decrease in the peak value of the cross section between ?6% and ?2% depending on the electron momentum transfer q² which has been varied between 2.5f ^?2 and 40f ^?2. These corrections are largest for smallq ²<5f ^?2. Furthermore the results show that the influence of our insufficient knowledge of the deuteron structure on the cross section is small.     

The production ofW + W − pairs in proton-antiproton colliders

We present the predictions of the Glashow-Weinberg-Salam [1] (GWS) model for the total cross-section and the angular and invariantmass differential cross sections for the reaction \(p\bar p \to W^ + W^ - X\) . We contrast these GWS predictions with those obtained by varying the anomalous magnetic moment of theW(κ), the analogue for theZWW coupling (κ _z ) and the relative strength of the γWW andZWW couplings (ω) from their GWS values. We find that changes in these parameters produce significant changes in both the total cross section and the angular and invariant mass differential cross sections. We also present the angular distribution of the decay leptons (W ⁺→/+v _l) and find in all cases it closely mirrors theW ⁺ angular distribution. We have given the intermediate results for the dominant quark subprocesses \((u\bar u \to W^ + W^ - ,d\bar d \to W^ + W^ - )\) .     

Scale breaking in inclusive charged particle production by e+e− annihilation

The scale cross section $\text{s}\text{d}\text{σ}\text{d}\text{x}{}_{\mathrm{<mtext>p</mtext>}}$ for inclusive charged-particle production in e⁺e^? annihilation has been studied for c.m. energies W between 12.0 and 36.7 GeV. Scale breaking is observed. For x_p>0.2 the cross section decreases by ≈20% when W increases from 14 to 35 GeV. The production angular distribution was used to separate the longitudinal and transverse cross-section contributions and to determine the ratio of the structure functions $\text{m}\text{W}{}_1$ and $\text{v}\text{W}{}_2$.     

Large p⊥ lepton production and the ψ(3100)

We determine the invariant cross section $\text{E}\text{d}\text{σ}\text{d}{}^3\text{p(s,x}{}_6\text{,pp}{}_{\mathrm{\perp }}\text{)}$ for pp→ψ(3100)+X near x₆=0 at NAL and ISR energies using the assumption that all large p_⊥ single leptons originate from the ψ. We adequately reproduce the single lepton data, and by suitable extrapolarion in x₆ ensure agreement with the NAL ψ production data (x₆?0.3). The magnitude of the resulting ψ production cross section is, however, roughly a factor of 3 larger than that observed by the recent CCRS-ISR experiment.     

Semi-inclusive deep inelastic lepton scattering in a pion cloud model

In this note we explore the consequences of the pion cloud model for semi-inclusive deep inelastic lepton scattering. We argue that by scattering on a few-nucleon target, the detection of the recoiling target would provide a valuable test of the meson cloud model. We estimate the semi-inclusive cross section for deep inelastic lepton scattering on a³He target, as function of Bjorkenx and target recoil momentum.     

Minimal total cross section fore + e −→W + W −

The total cross section with the most general form for the gauge boson vertices is given at tree level for the processe ⁺ e ^?→W ⁺ W ^?. Each vertex is parametrized with 7 couplings and the minimum of the total cross section is studied in a wide energy range. Although there are large cancellations between the neutrino exchange diagram and the photon andZ annihilation diagrams, it is surprisingly not possible to get significantly below the standard model cross section for any value of the parameters.     

The p + p → π+ + d reaction close to threshold at COSY

Differential and total cross sections of the p + p → π⁺ + d reaction close to threshold were measured employing a magnetic spectrograph with track reconstruction, a very thin liquid hydrogen target and an accelerated proton beam with high phase space density. The data resolve a previous discrepancy between the n + p → π⁰ + d and the π⁺ + d → 2p reaction close to threshold indicating that isospin symmetry may be broken in the s-wave part of the cross section.     

The decay of theτ lepton to six pions

We present the branching ratio predictions of an isospin statistical model forτ decays to four, five and six pions. Limits on the branching ratios of the three possible six pionτ decay modes using the Conserved Vector Current (CVC) Hypothesis and thee ⁺ e ^?→6π cross section data are also presented. We find that the isospin model prediction is in good agreement with the well-measured four pion decay modes and consistent with the five pion decay modes. However, we find that some of the recent six pionτ measurements do not agree with the isospin model and the CVC prediction.     

Jet analysis in lepton-hadron scattering from QCD

For deep inelastic lepton-hadron scattering we deduce from QCD perturbation theory the cross sections $\text{d}\text{σ}\text{d}\text{T}$ and $\text{d}\text{σ}\text{d}\text{S}$ in terms of the collective jet variables thrust T and spherocity S. We find that the shape of these cross sections depends mainly on the total hadronic energy W. While present data are consistent with the cross sections calculated they do not yet prove or disprove the presence of three-jet contributions. We predict that these contributions will be clearly visible for W ? 12 to 15 GeV.     

Investigation of anomalous four-boson couplings in photon-photon collisions at high energies

Anomalous four-boson couplings can be studied in the production of two or three bosons in γγ collisions at high energies. The dependence of the cross section for W ⁺ W ^? production on three anomalous couplings is studied at the TESLA energies (√s～1 TeV). A comprehensive analysis of anomalous contributions to the cross section and angular distributions for the process under consideration is presented.     

Production ofW-bosons in high energye + e − ande − p collisions

We study the processe ⁺ e ^?→W+hadrons from theZ ⁰-pole to the threshold region forW-pair production, keeping the widths of theZ ⁰ andW finite. Already slightly below threshold the cross section is strongly depressed. Also the total cross section at theZ ⁰-peak is very small. We present a simple model to account for this. We also give exact results to lowest order for the weak Compton processese ⁺ e ^?→e ⁺ W ^? v _e ande ^? p→pW ^? v _e and compare them with results obtained with the equivalent photon approximation.     

An analysis of prompt lepton emission at ISR energies

The e/π ratios at low p_T observed in pp collisions at √s = 53 GeV are analysed as a function of R, the ratio of the total number of electrons integrated over electron energies to the total number of pions integrated over pion energies. It is found that R is independent of the decay kinematics and very insensitive to the production dynamics of the parent particles. The total parent cross section times the branching ratio into an electron is calculated, and the result is interpreted as either the total inclusive cross section for production of charmed particles, or as the total cross section for single photons in pp collisions.     

Measurements of inclusive pion electroproduction

Measurements of the inclusive pion electroproduction reaction e^?+p → e^?+π^±+X made at the Wilson Synchrotron Laboratory are reported. Data were taken at points with nominal (Q², W) values of (0.6, 2.67), (1.2, 2.67), (2.0, 2.67) and (1.2, 2.15) in (GeV², GeV). A more complete angular distribution was taken at (1.2, 2.67). The virtual photoproduction cross section for π⁺ + missing mass is studied as a function of missing mass, Feynman scaling variables, Q² and W. The invariant cross section show a simple behavior as a function of Q² and W. Its dependenc on P_⊥², x′ and φ is determined.     

Formation of η′(958) Meson Bound States and Chiral Symmetry In-Medium

We theoretically discuss the feasibility to observe the η′(958)-mesic nuclei by using the missing mass spectroscopy. We evaluate the η′-nucleus optical potential including the contribution of lowest order in density together with the second order terms account for η′ absorption by two nucleons, based on a recent model of the η′N interaction. We show the calculated formation cross section of the η′ bound states from (π, N) reaction with pion beam momentum p _π = 1.8 GeV/c and (p, d) reaction with proton kinetic energy T _p = 2.5 GeV.