291 research outputs found

### Limits on deeply penetrating particles in the >10^17 eV cosmic-ray flux

Journal ArticleWe report on a search for deeply penetrating particles in the > 10^17 eV cosmic-ray flux using the University of Utah Fly's Eye detector. No such events have been found in 6 x 106 sec of running time. We consequently set limits on the following: quark matter in the primary cosmic-ray flux, high-energy long-lived weakly interacting particles produced in proton-air interactions, such as τ's; astrophysical neutrino flux; and other hypothetical high-energy weakly interacting components of the cosmic-ray flux such as photinos

### Evidence for a high-energy cosmic-ray spectrum cutoff

Journal ArticleWe report a measurement of the ultrahigh-energy cosmic-ray spectrum using an atmospheric fluorescence technique for extensive-air-shower detection. The differential spectrum between 0.1 and 10 EeV (1 EeV = 10^18 eV) is well fitted by a power law with slope 2.94 ±0.02. Above 10 EeV evidence is presented for the development of a spectral " bump " followed by a cutoff at 70 EeV

### Predicting Proton-Air Cross Sections at sqrt s ~30 TeV, using Accelerator and Cosmic Ray Data

We use the high energy predictions of a QCD-inspired parameterization of all
accelerator data on forward proton-proton and antiproton-proton scattering
amplitudes, along with Glauber theory, to predict proton-air cross sections at
energies near \sqrt s \approx 30 TeV. The parameterization of the proton-proton
cross section incorporates analyticity and unitarity, and demands that the
asymptotic proton is a black disk of soft partons. By comparing with the p-air
cosmic ray measurements, our analysis results in a constraint on the inclusive
particle production cross section.Comment: 9 pages, Revtex, uses epsfig.sty, 5 postscript figures. Minor text
revisions. Systematic errors in k included, procedure for extracting k
clarified. Previously undefined symbols now define

### The Elusive p-air Cross Section

For the \pbar p and $pp$ systems, we have used all of the extensive data of
the Particle Data Group[K. Hagiwara {\em et al.} (Particle Data Group), Phys.
Rev. D 66, 010001 (2002).]. We then subject these data to a screening process,
the ``Sieve'' algorithm[M. M. Block, physics/0506010.], in order to eliminate
``outliers'' that can skew a $\chi^2$ fit. With the ``Sieve'' algorithm, a
robust fit using a Lorentzian distribution is first made to all of the data to
sieve out abnormally high \delchi, the individual i$^{\rm th}$ point's
contribution to the total $\chi^2$. The $\chi^2$ fits are then made to the
sieved data. We demonstrate that we cleanly discriminate between asymptotic
$\ln s$ and $\ln^2s$ behavior of total hadronic cross sections when we require
that these amplitudes {\em also} describe, on average, low energy data
dominated by resonances. We simultaneously fit real analytic amplitudes to the
``sieved'' high energy measurements of $\bar p p$ and $pp$ total cross sections
and $\rho$-values for $\sqrt s\ge 6$ GeV, while requiring that their asymptotic
fits smoothly join the the $\sigma_{\bar p p}$ and $\sigma_{pp}$ total cross
sections at $\sqrt s=$4.0 GeV--again {\em both} in magnitude and slope. Our
results strongly favor a high energy $\ln^2s$ fit, basically excluding a $\ln
s$ fit. Finally, we make a screened Glauber fit for the p-air cross section,
using as input our precisely-determined $pp$ cross sections at cosmic ray
energies.Comment: 15 pages, 6 figures, 2 table,Paper delivered at c2cr2005 Conference,
Prague, September 7-13, 2005. Fig. 2 was missing from V1. V3 fixes all
figure

### Electromagnetic form factors in the J/\psi mass region: The case in favor of additional resonances

Using the results of our recent analysis of e^+e^- annihilation, we plot the
curves for the diagonal and transition form factors of light hadrons in the
time-like region up to the production threshold of an open charm quantum
number. The comparison with existing data on the decays of J/\psi into such
hadrons shows that some new resonance structures may be present in the mass
range between 2 GeVand the J/\psi mass. Searching them may help in a better
understanding of the mass spectrum in both the simple and a more sophisticated
quark models, and in revealing the details of the three-gluon mechanism of the
OZI rule breaking in K\bar K channel.Comment: Formulas are added, typo is corrected, the text is rearranged.
Replaced to match the version accepted in Phys Rev

### On the measurement of the proton-air cross section using longitudinal shower profiles

In this paper, we will discuss the prospects of deducing the proton-air cross
section from fluorescence telescope measurements of extensive air showers. As
it is not possible to observe the point of first interaction $X_{\rm 1}$
directly, other observables closely linked to $X_{\rm 1}$ must be inferred from
the longitudinal profiles. This introduces a dependence on the models used to
describe the shower development. The most straightforward candidate for a good
correlation to $X_{\rm 1}$ is the depth of shower maximum $X_{\rm max}$. We
will discuss the sensitivity of an $X_{\rm max}$-based analysis on $\sigma_{\rm
p-air}$ and quantify the systematic uncertainties arising from the model
dependence, parameters of the reconstruction method itself and a possible
non-proton contamination of the selected shower sample.Comment: 4 pages, Proceedings for ISVHECRI Weihei 200

### Arrival directions of cosmic rays of E .4 EeV

The anisotropy of cosmic rays observed by the Utah Fly's Eye detector has been studied. Emphasis has been placed on examining distributions of events in galactic coordinates. No statistically significant departure from isotropy has been observed for energies greater than 0.4 EeV (1 EeV = 10 to the 18th power eV). Results of the standard harmonic analysis in right ascension are also presented

### The structure of EAS at E 0.1 EeV

The ratio of extensive air showers (EAS) total shower energy in the electromagnetic channel (E em) to the size of the shower at maximum development (N max) from a direct measurement of shower longitudinal development using the air fluorescence technique was calculated. The values are not inconsistent with values based upon track length integrals of the Gaisser-Hillas formula for shower development or the known relation between shower energy and size at maximum for pure electromagnetic cascades. Using Linsley's estimates for undetected shower energy based on an analysis of a wide variety of cosmic ray data, the following relation for total shower energy E vs N max is obtained. The Gaisser Hillas implied undetected shower energy fractions

### Consequences of the Factorization Hypothesis in pbar p, pp, gamma p and gamma gamma Collisions

Using an eikonal analysis, we examine the validity of the factorization
theorem for nucleon-nucleon, gamma p and gamma gamma collisions. As an example,
using the additive quark model and meson vector dominance, we directly show
that for all energies and values of the eikonal, that the factorization theorem
sigma_{nn}/sigma_{gamma p} = sigma_{gamma p}/sigma_{gamma gamma} holds. We can
also compute the survival probability of large rapidity gaps in high energy
pbar p and pp collisions. We show that the survival probabilities are identical
(at the same energy) for gamma p and gamma gamma collisions, as well as for
nucleon-nucleon collisions. We further show that neither the factorization
theorem nor the reaction-independence of the survival probabilities depends on
the assumption of an additive quark model, but, more generally, depends on the
opacity of the eikonal being independent of whether the reaction is n-n, gamma
p or gamma gamma.Comment: 8 pages, Revtex, no figures. Expanded discussion, minor correction

### All sky Northern Hemisphere 10(15) EV gamma-ray survey

Flux limits in the range 10 to the minus 13th power-10 to the minus 12 power/sq cm/s have been obtained by observing Cerenkov flashes from small air showers. During 1983, a 3.5 sigma excess of showers was observed during the phase interval 0.2 to 0.3 of the 4.8h period of Cygnus X-3, but no excess was found in 1984 observations

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