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Cosmic Rays and Hadronic Interactions
Abstract
The cosmic ray spectrum extends to particles with energy
E ∼ 1020 eV, that corresponds (assuming that the primary particle is a proton) to a nucleon–nucleon c.m. energy
s
≃430
TeV
, 50 times higher than the current LHC
energy. These very high energy particles can be studied via the observation of the showers they generate in the atmosphere. The interpretation of the data requires therefore the modeling of hadronic interactions in an energy range beyond what can be studied in accelerator experiments. The theoretical problem of estimating the relevant properties of hadronic interactions in this energy range is therefore of central importance for the interpretation of the cosmic ray data. Viceversa, it is in principle possible to obtain information about hadronic interactions from the cosmic ray observations, but this program has to confront the fact that the (freely available) cosmic ray beam has an unknown energy
spectrum and an unknown mass composition.
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Observations of ultra high energy cosmic rays by extensive air showers rely on correct modeling of hadronic interaction in the forward region at very high energy. Recent new data from the LHC, especially for forward particle production, are important for a precise understanding of air shower development. In this article recent forward production data from p-p, p-Pb, and Pb-Pb collisions at LHC are reviewed.
The LHCf experiment is one of the LHC forward experiments. The aim of LHCf is to provide critical calibration data of hadronic intraction models used in air shower simulations. The LHCf has completed the operations for p-p collisions with a collision energy of √s = 0.9 and 7 TeV p-p in 2010 and for p-Pb collisions with a collision energy per nucleon of √sNN = 5.02. The recent LHCf result of forward neutron energy spectra at 7 TeV p-p collision and forward π0 spectra at p-Pb collisions are presented in this paper.
Currently the uncertainty in the prediction of shower observables for different primary particles and energies is dominated by differences between hadronic interaction models. The LHC data on minimum bias measurements can be used to test Monte Carlo generators and these new constraints will help to reduce the uncertainties in air shower predictions. In this article, after a short introduction on air showers and Monte Carlo generators, we will show the results of the comparison between the updated version of high energy hadronic interaction models EPOS LHC and QGSJETII-04 with LHC data. Results for air shower simulations and their consequences on comparisons with air shower data will be discussed.
This review of atmospheric muons and neutrinos emphasizes the high energy
range relevant for backgrounds to high-energy neutrinos of astrophysical
origin. After a brief historical introduction, the main distinguishing features
of atmospheric $\nu_\mu$ and $\nu_e$ are discussed, along with the implications
of the muon charge ratio for the $\nu_\mu/\bar{\nu}_\mu$ ratio. Methods to
account for effects of the knee in the primary cosmic-ray spectrum and the
energy-dependence of hadronic interactions on the neutrino fluxes are discussed
and illustrated in the context of recent results from IceCube. A simple
numerical/analytic method is proposed for systematic investigation of
uncertainties in neutrino fluxes arising from uncertainties in the primary
cosmic-ray spectrum/composition and hadronic interactions.
HEP event generators aim to describe high-energy collisions in full exclusive
detail. They combine perturbative matrix elements and parton showers with
dynamical models of less well-understood phenomena such as hadronization,
diffraction, and the so-called underlying event. We briefly summarise some of
the main concepts relevant to the modelling of soft/inclusive hadron
interactions in MC generators, in particular PYTHIA, with emphasis on questions
recently highlighted by LHC data.
We present a phenomenological approach (EPOS), based on the parton model, but going much beyond by incorporating elastic and inelastic parton ladder splitting. Based on this model, we try to understand proton-proton and deuteron-gold (dAu) collisions, in particular the rapidity dependence of transverse momentum results in dAu from all four experiments conducted on the BNL Relativistic Heavy Ion Collider.
The data collected by ATIC, PPB-BETS, FERMI-LAT and HESS all indicate that there is an electron/positron excess in the cosmic ray energy spectrum above ~100 GeV, although different instrumental teams do not agree on the detailed spectral shape. PAMELA also reported clearly the excessive feature of the fraction of positron above several GeV, but with no excess in antiprotons. Here we review the observational status and theoretical models of this interesting observational feature. We pay special attention to various physical interpretations proposed in the literature, including modified supernova remnant models for the e± background, new astrophysical sources, and new physics (the dark matter models). We suggest that although most models can make a case to interpret the data, with the current observational constraints the dark matter interpretations, especially those invoking annihilation, require much more exotic assumptions than some other astrophysical interpretations. Future observations may present some "smoking-gun" observational tests to differentiate different models and to identify the correct interpretation of the phenomenon.
The cosmic ray interaction event generator Sibyll is widely used in extensive air shower simulations. We describe in detail the properties of Sibyll 2.1 and the differences with the original version 1.7. The major structural improvements are the possibility to have multiple soft interactions, introduction of new parton density functions, and an improved treatment of diffraction. Sibyll 2.1 gives better agreement with fixed target and collider data, especially for the inelastic cross sections and multiplicities of secondary particles. Shortcomings and suggestions for future improvements are also discussed.
Observations of extensive air showers in the atmosphere obtained with the fly's-eye detector at the University of Utah by the atmospheric-fluorescence technique are used to determine the proton-air inelastic cross section (PAICS) at (sq rt s) = 30 TeV. The data-cutting and analysis procedures are described in detail and illustrated graphically. The distribution of shower maxima as a function of atmospheric depth is found to exhibit an exponential tail of slope 72 + or - 9 g/sq cm, corresponding to PAICS = 530 + or - 66 mb. A proton-proton total cross section (PPTCS) of 120 + or -15 mb is then obtained, using the theoretical model of Glauber and Matthias (1970) and a Gaussian nucleus distribution and assuming that the nuclear slope parameter is proportional to PPTCS.
We conduct a review of experimental results on ultra-high energy cosmic rays (UHECRs) including measurements of the features of the spectrum, the composition of the primary particle flux and the search for anisotropy in event arrival direction. We find that while there is a general consensus on the features in the spectrum---the Second Knee, the Ankle and (to a lesser extent) the GZK Cutoff---there is little consensus on the composition of the primaries that accompany these features. This lack of consensus on the composition makes interpretation of the agreed upon features problematic. There is also little direct evidence about potential sources of UHECRs, as early reports of arrival-direction anisotropies have not been confirmed in independent measurements.
The pseudorapidity density and multiplicity distribution of charged particles produced in proton-proton collisions at the LHC, at a centre-of-mass energy root s = 7 TeV, were measured in the central pseudorapidity region vertical bar eta vertical bar < 1. Comparisons are made with previous measurements at root s = 0.9 TeV and 2.36 TeV. At root s = 7 TeV, for events with at least one charged particle in |eta vertical bar| < 1, we obtain dN(ch)/d eta = 6.01 +/- 0.01(stat.)(-0.12)(+0.20) (syst.). This corresponds to an increase of 57.6%+/-0.4%(stat.)(-1.8%)(+3.6) (syst.) relative to collisions at 0.9 TeV, significantly higher than calculations from commonly used models. The multiplicity distribution at 7 TeV is described fairly well by the negative binomial distribution.
We study the spectrum and average mass composition of cosmic rays with primary energies between 10^{17} and 10^{18} eV using a hybrid detector consisting of the High Resolution Fly's Eye (HiRes) prototype and the Michigan Muon Array (MIA). Measurements have been made of the change in the depth of shower maximum as a function of energy. A complete Monte Carlo simulation of the detector response and comparisons with shower simulations leads to the conclusion that the cosmic-ray intensity is changing from a heavier to a lighter composition in this energy range. The spectrum is consistent with earlier Fly's Eye measurements and supports the previously found steepening near 4 × 10^{17} eV.
We discuss expectations for the total and inelastic cross-sections at LHC CM
energies $\sqrt{s}\ =\ 7\ TeV$ {and $ 14\ TeV$} obtained in an eikonal minijet
model augmented by soft gluon $k_t$-resummation, which we describe in some
detail. We present a band of predictions which encompass recent LHC data and
suggest that the inelastic cross-section described by two channel eikonal
models include only uncorrelated processes. We show that this interpretation of
the model is supported by the LHC data.
The purpose of The Telescope Array experiment is to identify origin of the ultra high energy cosmic rays. The Telescope Array is a hybrid detector consists of a surface detector array and air fluorescence detectors. This hybrid detector is observing extensive air showers to measure the energy spectrum, anisotropy and composition of Ultra High Energy Cosmic Rays. The detector construction has been completed in March 2008, and the hybrid observation with the full configuration has been running since that time. In this talk, the status of observation and our prospects are described.
Measurements are presented from proton–proton collisions at centre-of-mass energies of , 2.36 and 7 TeV recorded with the ATLAS detector at the LHC. Events were collected using a single-arm minimum-bias trigger. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the relationship between the mean transverse momentum and charged-particle multiplicity are measured. Measurements in different regions of phase space are shown, providing diffraction-reduced measurements as well as more inclusive ones. The observed distributions are corrected to well-defined phase-space regions, using model-independent corrections. The results are compared to each other and to various Monte Carlo (MC) models, including a new AMBT1 pythia6 tune. In all the kinematic regions considered, the particle multiplicities are higher than predicted by the MC models. The central charged-particle multiplicity per event and unit of pseudorapidity, for tracks with pT>100 MeV, is measured to be 3.483±0.009 (stat)±0.106 (syst) at and 5.630±0.003 (stat)±0.169 (syst) at .
This paper describes measurements of the sum of the transverse energy of
particles as a function of particle pseudorapidity, eta, in proton-proton
collisions at a centre-of-mass energy, sqrt(s) = 7 TeV using the ATLAS detector
at the Large Hadron Collider. The measurements are performed in the region
|eta| < 4.8 for two event classes: those requiring the presence of particles
with a low transverse momentum and those requiring particles with a significant
transverse momentum. In the second dataset measurements are made in the region
transverse to the hard scatter. The distributions are compared to the
predictions of various Monte Carlo event generators, which generally tend to
underestimate the amount of transverse energy at high |eta|.
The inclusive photon energy spectra measured by the Large Hadron Collider
forward (LHCf) experiment in the very forward region of LHC proton-proton
collisions at $\sqrt{s}=$ 900 GeV are reported. The results from the analysis
of 0.30 $\mathrm{nb^{-1}}$ of data collected in May 2010 in the two
pseudorapidity regions of $\eta > 10.15$ and $8.77 < \eta < 9.46$ are compared
with the predictions of the hadronic interaction models DPMJET 3.04, EPOS 1.99,
PYTHIA 8.145, QGSJET I -.1em I-03 and SIBYLL 2.1, which are widely used in
ultra-high-energy cosmic-ray experiments. EPOS 1.99 and SYBILL 2.1 show a
reasonable agreement with the spectral shape of the experimental data, whereas
they predict lower cross-sections than the data. The other models, DPMJET 3.04,
QGSJET I -.1em I-03 and PYTHIA 8.145, are in good agreement with the data below
300 GeV but predict harder energy spectra than the data above 300 GeV. The
results of these comparisons exhibited features similar to those for the
previously reported data for $\sqrt{s}=$ 7 TeV collisions.
The Telescope Array (TA) collaboration has measured the energy spectrum of
ultra-high energy cosmic rays with primary energies above 1.6 x 10^(18) eV.
This measurement is based upon four years of observation by the surface
detector component of TA. The spectrum shows a dip at an energy of 5 x 10^(18)
eV and a steepening at 5 x 10^(19) eV which is consistent with the expectation
from the GZK cutoff. We present the results of a technique, new to the analysis
of ultra-high energy cosmic ray surface detector data, that involves generating
a complete simulation of ultra-high energy cosmic rays striking the TA surface
detector. The procedure starts with shower simulations using the CORSIKA Monte
Carlo program where we have solved the problems caused by use of the "thinning"
approximation. This simulation method allows us to make an accurate calculation
of the acceptance of the detector for the energies concerned.
The inclusive production rate of neutral pions in the rapidity range greater
than $y=8.9$ has been measured by the Large Hadron Collider forward (LHCf)
experiment during LHC $\sqrt{s}=7$\,TeV proton-proton collision operation in
early 2010. This paper presents the transverse momentum spectra of the neutral
pions. The spectra from two independent LHCf detectors are consistent with each
other and serve as a cross check of the data. The transverse momentum spectra
are also compared with the predictions of several hadronic interaction models
that are often used for high energy particle physics and for modeling
ultra-high-energy cosmic-ray showers.
The TOTEM experiment has measured the charged particle pseudorapidity density
dN_{ch}/deta in pp collisions at √s = 7 TeV for 5.3<|eta|<6.4 in events
with at least one charged particle with transverse momentum above 40 MeV/c in
this pseudorapidity range. This extends the analogous measurement performed by
the other LHC experiments to the previously unexplored forward eta region. The
measurement refers to more than 99% of non-diffractive processes and to single
and double diffractive processes with diffractive masses above ~3.4 GeV/c^2,
corresponding to about 95% of the total inelastic cross-section. The
dN_{ch}/deta has been found to decrease with |eta|, from 3.84 pm 0.01(stat) pm
0.37(syst) at |eta| = 5.375 to 2.38 pm 0.01(stat) pm 0.21(syst) at |eta| =
6.375. Several MC generators have been compared to data; none of them has been
found to fully describe the measurement.
We have searched for correlations between the pointing directions of ultrahigh energy cosmic rays observed by the High Resolution Fly’s Eye experiment and active galactic nuclei (AGN) visible from its northern hemisphere location. No correlations, other than random correlations, have been found. We report our results using search parameters prescribed by the Pierre Auger collaboration. Using these parameters, the Auger collaboration concludes that a positive correlation exists for sources visible to their southern hemisphere location. We also describe results using two methods for determining the chance probability of correlations: one in which a hypothesis is formed from scanning one half of the data and tested on the second half, and another which involves a scan over the entire data set. The most significant correlation found occurred with a chance probability of 24%.
There are both theoretical and experimental uncertainties in using data from cosmic-ray air showers to estimate hadronic cross sections above accelerator energies. We outline these problems and compare the physics used to extract σtotpp from air shower data to the widely used parametrization of the proton-proton cross section of Donnachie and Landshoff and other contemporary models. We conclude that the published cosmic-ray cross section values do not strongly constrain σtotpp fits from lower energy accelerator data.
1. Introduction.- 2. Preliminaries.- 3. Kinematics.- 4. The Relativistic S-Matrix.- 5. Regge Theory.- 6. Geometrical and s-Channel Models.- 7. Soft Diffraction: a Phenomenological Survey.- 8. The Pomeron in QCD.- 9. Deep Inelastic Scattering.- 10. Phenomenology of Hard Diffraction.- 11. Hard Diffraction in QCD.- A. Conventions.- A.1 Four-Vectors.- A.2 Sudakov Parametrization.- A.3 Reference Frames.- A.4 Fermionic States.- B. Mellin Transforms.- C. QCD Formulas.- C.2 Feynman Rules for QCD.- References.
The mysterious “radiation ... entering our atmosphere from above” discovered by Hess in 1912 is now known to be dominated by relativistic charged particles, mostly with energies in the GeV-range, but extending to energies higher by many orders of magnitude. As none of these particles can penetrate the earth’s atmosphere without interaction, detailed studies of their composition and energy spectra require observations with high-altitude balloons or spacecraft. This became possible only towards the middle of the 20th century. The direct measurements have now revealed much detail about the Galactic cosmic rays below 1015eV, but do not yet provide much overlap with the air-shower region of energies. A historic overview of the measurements is given, beginning with the realization that the majority of the cosmic rays are protons. The discovery and astrophysical significance of the heavier nuclei, and of the ultra-heavy nuclei beyond iron and up to the actinides, are then described, and measurements of the isotopic composition are discussed. Observations of the individual energy spectra are reviewed, and finally, the detection of electrons, positrons, and anti-protons in the cosmic rays, and the searches for exotic or unusual phenomena are summarized. Emphasis is given to the fact that all of these discoveries have become possible through the evolution of increasingly sophisticated detection techniques, a process that is continuing through the present time. The precise knowledge of the abundance distributions of the elements in the cosmic rays and of their isotopic composition permits a comparison with the “universal abundance scale” and provides strong constraints on the origin of the cosmic-ray material in the interstellar medium. “Clock-isotopes” reveal the time history of the particles. The shapes of the energy spectra of the individual cosmic-ray components are related to evolving ideas about particle acceleration and propagation in the Galaxy. In conclusion, prospects for future work are briefly discussed.
Data collected by the Pierre Auger Observatory through 31 August 2007 showed evidence for anisotropy in the arrival directions of cosmic rays above the Greisen-Zatsepin-Kuzmin energy threshold, 6 x 10{sup 19} eV. The anisotropy was measured by the fraction of arrival directions that are less than 3.1{sup o} from the position of an active galactic nucleus within 75 Mpc (using the Veron-Cetty and Veron 12th catalog). An updated measurement of this fraction is reported here using the arrival directions of cosmic rays recorded above the same energy threshold through 31 December 2009. The number of arrival directions has increased from 27 to 69, allowing a more precise measurement. The correlating fraction is (38{sub -6}{sup +7})%, compared with 21% expected for isotropic cosmic rays. This is down from the early estimate of (69{sub -13}{sup +11})%. The enlarged set of arrival directions is examined also in relation to other populations of nearby extragalactic objects: galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in hard X-rays by the Swift Burst Alert Telescope. A celestial region around the position of the radiogalaxy Cen A has the largest excess of arrival directions relative to isotropic expectations. The 2-point autocorrelation function is shown for the enlarged set of arrival directions and compared to the isotropic expectation.
A phenomenon is predicted in which a high-energy particle beam undergoing diffraction scattering from a nucleus will acquire components corresponding to various products of the virtual dissociations of the incident particle, as p-->Lambda+K+ or pi--->p¯+n. These diffraction-produced systems would have a characteristic extremely narrow distribution in transverse momentum, and would have all the same quantum numbers as the initial particle; i.e., the same spin, isotopic spin, and parity. The process is related to that discussed in the preceding paper, and has the same effective energy threshold.
A model is analyzed that provides a parametrization of the properties of the jet of mesons generated by a fast outgoing quark. It is assumed that the meson that contains the original quark leaves momentum and flavor to a remaining jet in which the particles are distributed (except for scaling of the energy and possible changes of flavor) like those of the original jet. One function, the probability f(eta) that the remaining jet has a fraction eta of the momentum of the original jet, is chosen (as a parabola) so the final distribution of charged hadrons agrees with data from lepton experiments. All the properties of quark jets are determined from f(eta) and three parameters; the degree that SU(3) is broken in the formation of new quark-antiquark pairs (ss is taken as half as likely as uu), the spin nature of the primary mesons (assumed to be vector and pseudoscalar with equal probability), and the mean transverse momentum given to these primary mesons. Monte Carlo methods are used to generate typical jets. Analytic approximations are also given. Many features of quark jets are examined. The distribution of momentum of various hadrons Dqh(z), the properties of the hadrons of largest momentum in the jet, correlations, rapidity-gap distribution of charge and of transverse momentum are some of the subjects discussed. The appearance of the jets to an instrument sensitive only to particles above some minimum momentum is also described. Although the model is probably not a true description of the physical mechanism responsible for quark jets, many predictions of the model seem quite reasonable, possibly much like real quark jets (except that the possibility of the emission of baryons is disregarded). The purpose of this work is to provide a model useful in the design of experiments in which quark jets may be observed, and further to provide a standard to facilitate the comparison of lepton-generated jets with the high-p⊥ jets found in hadron collisions.
It is proved that a two-body reaction amplitude involving scalar particles and satisfying Mandelstam's representation is bounded by expressions of the form Csln2s at the forward and backward angles, and Cs34ln32s at any other fixed angle in the physical region, C being a constant, s being the total squared c.m. energy. This corresponds to cross sections increasing at most like ln2s. These restrictions limit the freedom of choice of the subtraction terms to six arbitrary single spectral functions and one subtraction constant.
We describe the measurement of the depth of maximum, Xmaxf , of the longitudinal development of air showers induced by cosmic rays. Almost 4000 events above 1018eV observed by the fluorescence detector of the Pierre Auger Observatory in coincidence with at least one surface detector station are selected for the analysis. The average shower maximum was found to evolve with energy at a rate of (106-21+35)g/cm2/decade below 1018.24±0.05eV, and (24±3)g/cm2/decade above this energy. The measured shower-to-shower fluctuations decrease from about 55 to 26g/cm2. The interpretation of these results in terms of the cosmic ray mass composition is briefly discussed. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Keywords (in text query field) Abstract Text Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints
Nonlinear effects in hadronic interactions are treated by means of enhanced Pomeron diagrams, assuming that Pomeron-Pomeron coupling is dominated by soft partonic processes. It is shown that the approach allows to resolve a seeming contradiction between realistic parton momentum distributions, measured in deep inelastic scattering experiments, and the energy behavior of total proton-proton cross section. Also a general consistency with both soft and hard diffraction data is demonstrated. An important feature of the proposed scheme is that the contribution of semihard processes to the interaction eikonal contains a significant nonfactorizable part. On the other hand, the approach preserves the QCD factorization picture for inclusive high-pt jet production.
We apply parton-model concepts to the "soft" (small-momentum-transfer) processes which make up the majority of the hadronic total cross section. Diffraction is calculated as the shadow of these soft processes. We obtain an attractive picture of the essential features of total, elastic, and diffractive-inelastic scattering. In particular, the rather large cross section for inelastic diffraction, which is observed experimentally, results from fluctuations in the distribution of the wee partons which initiate interactions. These fluctuations lead to diffractive production by the mechanism of Good and Walker. The observed peripheral character of diffraction as a function of impact parameter, the absence of a forward dip in dσ/dtdm2, the correct integrated cross section, and the correct small-t slope of diffraction all follow naturally in our approach.
Fits to high energy data alone cannot cleanly discriminate between
asymptotic $\ln s$ and $\ln^2s$ behavior of total hadronic cross
sections. We demonstrate that this is no longer true when we require
that these amplitudes also describe, on average, low energy data
dominated by resonances.
Not Available
Present address: DESY, Theory Group, Notkestrasse 85, D-2000 Hamburg 52,
Germany.
Contents: (1) Why bother with ultra-high-energy cosmic rays? (2)
Observational data: Energy spectrum and composition of high-energy
particles. Observed anisotropy of high-energy cosmic rays. Specific
identified sources of cosmic rays. (3) Acceleration mechanisms: Problems
associated with statistical acceleration. Direct acceleration. Final
comments. (4) Propagation of cosmic rays: Propagation from extragalactic
sources. Propagation from galactic sources. (5) Conclusions.
The central idea of diffusive shock acceleration is presented from microscopic and macroscopic viewpoints; applied to reactionless test particles in a steady plane shock the mechanism is shown to produce a power law spectrum in momentum with a slope which, to lowest order in the ratio of plasma to particle speed, depends only on the compression in the shock. The associated time scale is found (also by a macroscopic and a microscopic method) and the problems of spherical shocks, as exemplified by a point explosion and a stellar-wind terminator, are treated by singular perturbation theory. The effect of including the particle reaction is then studied. It is shown that if the scattering is due to resonant waves these can rapidly grow with unknown consequences. The possible steady modified shock structures are classified and generalised Rankine-Hugoniot conditions found. Modifications of the spectrum are discussed on the basis of an exact, if rather artificial, solution, a high-energy asymptotic expansion and a perturbation expansion due to Blandford. It is pointed out that no steady solution can exist for very strong shocks; the possible time dependence is briefly discussed.
We report new measurements of the isotopic abundances of the Galactic cosmic-ray isotopes 7Be,9Be, and radioactive 10Be. These measurements from the Ulysses High Energy Telescope (HET) combine exceptional mass resolution with superior statistics. Measurements of radioisotopes produced as secondaries during cosmic-ray propagation provide estimates of the average density of material traversed by the cosmic rays and, within the context of the "leaky box" model, the confinement time of cosmic rays in the Galaxy. 10Be, with its long lifetime (τ½=1.6 × 106 yr by β− decay) and pure secondary origin, is particularly well suited to this purpose. The HET measurement yields a density of ρ=0.19 ± 0.03 atoms cm-3, corresponding to a confinement time of 26+ 4−5 Myr. Measurements of the shorter lived cosmic-ray radioisotopes 26Al and 36Cl, including the results from the HET reported elsewhere (by Connell and coworkers), complement these 10Be results and provide a broader view of cosmic-ray propagation.
The mass composition of high energy cosmic rays depends on their production,
acceleration, and propagation. The study of cosmic ray composition can
therefore reveal hints of the origin of these particles. At the South Pole, the
IceCube Neutrino Observatory is capable of measuring two components of cosmic
ray air showers in coincidence: the electromagnetic component at high altitude
(2835 m) using the IceTop surface array, and the muonic component above ~1 TeV
using the IceCube array. This unique detector arrangement provides an
opportunity for precision measurements of the cosmic ray energy spectrum and
composition in the region of the knee and beyond. We present the results of a
neural network analysis technique to study the cosmic ray composition and the
energy spectrum from 1 PeV to 30 PeV using data recorded using the
40-string/40-station configuration of the IceCube Neutrino Observatory.
We present a ‘new generation’ model for high energy proton–proton ‘soft’ interactions. It allows for a full set of multipomeron
vertices as well as for including multichannel eikonal scattering. It describes the behaviour of the proton–proton total,
σtot, and elastic, dσel/dt, cross sections together with those for low- and high-mass proton dissociation. Although the model contains a comprehensive
set of multipomeron diagrams, it has a simple partonic interpretation. Including the more complicated multipomeron vertices
reduces the absorptive effects as compared to the predictions in which only the triple-pomeron vertex is considered. Tuning
the model to describe the available ‘soft’ data in the CERN ISR–tevatron energy range, we predict the total, elastic, single-
and double-diffractive dissociation cross sections at the LHC energy. An inescapable consequence of including multichannel
eikonal and multipomeron effects is that the total cross section is expected to be lower than before: indeed, we find σtot≃ 90mb at the LHC energy. We also present differential forms of the cross sections. In addition, we calculate soft diffractive
central production.
The single diffractive component in hadronhadron interactions is studied in the two-component Dual Parton Model. We distinguish high mass single diffraction represented by a triple-Pomeron exchange and low mass single diffraction described via a two channel eikonal method. The calculated single diffractive cross sections, and the distributions agree quite well with data from collider and fixed target experiments. The fit of the model parameters to cross section data gives a extrapolation of the total, elastic, and single diffractive cross sections to supercollider energies which depends on the parton structure functions used for the minijet component.
We parametrize TOTEM data for the elastic differential pp cross section at
sqrt(s)=7 TeV in terms of two exponentials with a relative phase. We employ two
previously derived sum rules for pp elastic scattering amplitude in impact
parameter space to check whether asymptotia has been reached at the LHC. A
detailed study of the TOTEM data for the elastic differential cross section at
sqrt(s)=7 TeV is made and it is shown that, within errors, the asymptotic sum
rules are satisfied at LHC. We propose to use this parametrization to study
forthcoming higher energy data.
We report a measurement of the flux of cosmic rays with unprecedented precision and statistics using the Pierre Auger Observatory. Based on fluorescence observations in coincidence with at least one surface detector we derive a spectrum for energies above 1018 eV. We also update the previously published energy spectrum obtained with the surface detector array. The two spectra are combined addressing the systematic uncertainties and, in particular, the influence of the energy resolution on the spectral shape. The spectrum can be described by a broken power law E−γ with index γ=3.3 below the ankle which is measured at log10(Eankle/eV)=18.6. Above the ankle the spectrum is described by a power law with index 2.6 followed by a flux suppression, above about log10(E/eV)=19.5, detected with high statistical significance.
A review of theoretical approaches to the problem of diffractive scattering at high energies is presented. A phenomenological analysis of experimental data on inelastic diffractive processes is carried out and the main properties of diffraction are discussed.
The knee in the all-particle energy spectrum is scrutinized with a phenomenological model, named poly-gonato model, linking results from direct and indirect measurements. For this purpose, recent results from direct and indirect measurements of cosmic rays in the energy range from 10 GeV up to 1 EeV are examined. The energy spectra of individual elements, as obtained by direct observations, are extrapolated to high energies using power laws and compared to all-particle spectra from air shower measurements. A cut-off for each element proportional to its charge Z is assumed. The model describes the knee in the all-particle energy spectrum as a result of subsequent cut-offs for individual elements, starting with the proton component at 4.5 PeV, and the second change of the spectral index around 0.4 EeV as due to the end of stable elements (Z=92). The mass composition, extrapolated from direct measurements to high energies, using the poly-gonato model, is compatible with results from air shower experiments measuring the electromagnetic, muonic, and hadronic components. But it disagrees with the mass composition derived from Xmax measurements using Čerenkov and fluorescence light detectors.
A composition analysis of KASCADE air shower data is performed by means of unfolding the two-dimensional frequency spectrum of electron and muon numbers. Aim of the analysis is the determination of energy spectra for elemental groups representing the chemical composition of primary cosmic rays. Since such an analysis depends crucially on simulations of air showers the two different hadronic interaction models QGSJet and SIBYLL are used for their generation. The resulting primary energy spectra show that the knee in the all particle spectrum is due to a steepening of the spectra of light elements but, also, that neither of the two simulation sets is able to describe the measured data consistently over the whole energy range with discrepancies appearing in different energy regions.
We discuss and present phenomenological evidence to support the hypothesis that several new phenomena observed in low-pt physics are due to the presence of low-x QCD jets in minimum bias physics. The phenomena we examine are KNO scaling violations, growth of 〈pt〉 with multiplicity and rise of the non-diffractive part of the total cross section.
I discuss a theory of non-solar cosmic rays (CRs) based on a single type of CR source at all energies. All observed properties of CRs are predicted in terms of very simple and completely 'standard' physics. The source of CRs is extremely 'economical': it has only one parameter to be fitted to the enormous ensemble of all of the data. All other inputs are 'priors', that is theoretical or observational items of information independent of the properties of the source of CRs and chosen to lie in their pre-established ranges.