120614937
Elastic scattering in nucleon-nucleon collisions
Recently, E811 has measured[1] the total cross section for pp scattering at √s = 1800 GeV. In this paper, we refit the experimental data for σtot, ϱ and B for both pp and pp to a QCD-inspired eikonal model, including the new σtot measurement.
121620095
Experimental observation of a copious yield of electrons with small transverse momenta in pp collisions at high energies
Abstract Inclusive electron and positron emission have been observed for θ cm = 30° and s = 2800 GeV 2 at the CERN Intersecting Storage Rings (ISR). Over the transverse momentum interval 0.2 GeV/ c p T c , electrons and positrons, which are equal in number within the experimental accuracies, appear to grow with respect to other particles (pions) approximately like 1/ p T . We are unable to explain their number and p T -dependence in terms of “conventional” mechanisms.
119621682
Ultra-high Energy Predictions of proton-air Cross Sections from Accelerator Data
M. M. Block Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208 We predict σ p−air, the proton–air inelastic production cross section, at pp center-of-mass energies 2 ≤ √ s ≤ 100000 TeV, using high energy predictions from a saturated Froissart bound parameterization of accelerator data on forward p̄p and pp scattering amplitudes, together with Glauber theory. The parameterization of the p̄p and pp cross sections incorporates analyticity constraints and unitarity, allowing accurate extrapolations to ultra-high energies. Our predictions are in excellent agreement with cosmic ray extensive air shower measurements, both in magnitude and in energy dependence.
95016103
A Liquid Helium Bubble Chamber
1) To provide an efficient dewar with large windows on two sides which allow for illuminating and photo­ graphing the bubble chamber tracks without the difficulty of any intervening liquid nitrogen or helium baths in the light path between the bubble chamber and the room temperature photographic system. At the same time heat losses due to room temperature radiation must be reduced several hundred times below that expected from two such room temperature windows.
119386557
Hadronic forward scattering : Predictions for the Large Hadron Collider and cosmic rays
Abstract The status of hadron–hadron interactions is reviewed, with emphasis on the forward and near-forward scattering regions. Using unitarity, the optical theorem is derived. Analyticity and crossing symmetry, along with integral dispersion relations, are used to connect particle–particle and antiparticle–particle total cross sections and ρ -values, e.g., σ pp , σ p ¯ p , ρ pp and ρ p ¯ p , where ρ is the ratio of the real to the imaginary portion of the forward scattering amplitude. Real analytic amplitudes are then introduced to exploit analyticity and crossing symmetry. Again, from analyticity, finite energy sum rules (FESRs) are introduced from which new analyticity constraints are derived. These new analyticity conditions exploit the many very accurate low-energy experimental cross sections, i.e., they constrain the values of the asymptotic cross sections and their derivatives at low energies just above the resonance regions, allowing us new insights into duality. A robust fitting technique—using a minimization of the Lorentzian squared followed by the “Sieve” algorithm—is introduced in order to ‘clean up’ large data samples that are contaminated by outliers, allowing us to make much better fits to hadron–hadron scattering data over very large regions of energy. Experimental evidence for factorization theorems for γ γ , γ p and nucleon–nucleon collisions is presented. The Froissart bound is discussed—what do we mean here by the saturation of the Froissart bound? Using our analyticity constraints, new methods of fitting high-energy hadronic data are introduced which result in much more precise estimates of the fit parameters, allowing accurate extrapolations to much higher energies. It's shown that the γ p , π ± p and nucleon–nucleon cross sections all go asymptotically as ln 2 s , saturating the bound, while conclusively ruling out ln s and s α ( α ∼ 0.08 ) behavior. Implications of this saturation for predictions of σ pp and ρ pp at the Large Hadron Collider (LHC) and for cosmic rays are given. We discuss present day cosmic ray measurements, what they measure and how they deduce p–air cross sections. Connections are made between very high-energy measurements of σ p – air prod —which have rather poor energy determination—and predictions of σ p – air prod obtained, using a Glauber model, from values of σ pp that are extrapolated from fits of accelerator data at very precisely known, albeit lower, energies.
121023736
PHASE-SPACE INTEGRALS FOR MULTIPARTICLE SYSTEMS
The total phase-space integrals, occurring in the Fermi statistical theory of meson production, for 2-, 3-, 4-, and 5-body final states are reduced to forms suitable for numerical evaluation by hand computation. In addition, the momentum spectrum of any one particle, as derived from the statistical factor, is evaluated. For the 3- and 4-body systems, the $Q$ distribution for any two of the particles (effective mass minus the rest masses of the 2-particle subsystem) is derived. Numerical results are presented for nucleon-nucleon collisions at 0.8-, 1.5-, and 2.7-Bev bombarding kinetic energies.
10030510
DUST PRODUCTION AND MASS LOSS IN THE GALACTIC GLOBULAR CLUSTER NGC 362
We investigate dust production and stellar mass loss in the Galactic globular cluster NGC 362. Due to its close proximity to the Small Magellanic Cloud (SMC), NGC 362 was imaged with the Infrared Array Camera and Multiband Imaging Photometer cameras onboard the Spitzer Space Telescope as part of the Surveying the Agents of Galaxy Evolution (SAGE-SMC) Spitzer Legacy program. We detect several cluster members near the tip of the red giant branch (RGB) that exhibit infrared excesses indicative of circumstellar dust and find that dust is not present in measurable quantities in stars below the tip of the RGB. We modeled the spectral energy distribution (SED) of the stars with the strongest IR excess and find a total cluster dust mass-loss rate of 3.0{sup +2.0}{sub -1.2} x 10{sup -9} M{sub sun} yr{sup -1}, corresponding to a gas mass-loss rate of 8.6{sup +5.6}{sub -3.4} x 10{sup -6} M{sub sun} yr{sup -1}, assuming [Fe/H] =-1.16. This mass loss is in addition to any dustless mass loss that is certainly occurring within the cluster. The two most extreme stars, variables V2 and V16, contribute up to 45% of the total cluster dust-traced mass loss. The SEDs of the more moderate stars indicate themore » presence of silicate dust, as expected for low-mass, low-metallicity stars. Surprisingly, the SED shapes of the stars with the strongest mass-loss rates appear to require the presence of amorphous carbon dust, possibly in combination with silicate dust, despite their oxygen-rich nature. These results corroborate our previous findings in omega Centauri.« less