Cosmic ray and gamma ray dosimetry for TL and ESR

We re-examine the X-ray luminosity–temperature relation using a nearly homogeneous data set of 24 clusters selected for statistically accurate temperature measurements and absence of strong cooling flows. The data exhibit a remarkably tight power-law relation between bolometric luminosity and temperature with a slope 2.88 ± 0.15. With reasonable assumptions regarding cluster structure, we infer an upper limit on fractional variations in the intracluster gas fraction 〈(δ fgas fgas)2〉1/2≤ 15 per cent. A strictly homogeneous Ginga subset of 18 clusters places a more stringent limit of 9 per cent.



Imaging data from the literature are employed to determine absolute values of fgas within spheres encompassing density contrasts δc=500 and 200 with respect to the critical density. Comparing binding mass estimates based on the virial theorem (VT) and the hydrostatic β-model (BM), we find a temperature-dependent discrepancy in fgas between the two methods caused by systematic variation of the outer slope parameter β with temperature. Mean values (for H0=50 km s−1 Mpc−1) range from f¯gas=0.10 for cool (T 4 keV) clusters using the BM at δc=200. There is evidence that cool clusters have a lower mean gas fraction than hot clusters, but it is not possible to assess the statistical significance of this effect in the present data set. The T dependence of the intracluster medium (ICM) density structure, coupled with the increase of the gas fraction with T in the VT approach, explains the steepening of the LX–T relation.



The small variation about the mean gas fraction within this majority subpopulation of clusters presents an important constraint for theories of galaxy formation and supports arguments against an Einstein–de Sitter universe based on the population mean gas fraction and conventional, primordial nucleosynthesis. The apparent trend of lower gas fractions and more extended atmospheres in low-temperature systems is consistent with expectations of models incorporating the effects of galactic winds on the ICM.

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The LX—T relation and intracluster gas fractions of X-ray clusters

The Great Pyramid or Khufu’s Pyramid was built on the Giza Plateau (Egypt) during the IVth dynasty by the pharaoh Khufu (Cheops), who reigned from 2509 to 2483 BC$^1$ . Despite being one of the oldest and largest monuments on Earth, there is no consensus about how it was built. To better understand its internal structure, we imaged the pyramid using muons, which are by-products of cosmic rays that are only partially absorbed by stone. The resulting cosmic-ray muon radiography allows us to visualize the known and potentially unknown voids in the pyramid in a non-invasive way. Here we report the discovery of a large void (with a cross section similar to the Grand Gallery and a length of 30m minimum) above the Grand Gallery, which constitutes the first major inner structure found in the Great Pyramid since the 19$^{th}$ century. This void, named ScanPyramids Big Void, was first observed with nuclear emulsion films installed in the Queen’s chamber (Nagoya University), then confirmed with scintillator hodoscopes set up in the same chamber (KEK) and re-confirmed with gas detectors12 outside of the pyramid (CEA)This large void has therefore been detected with a high confidence by three different muon detection technologies and
three independent analyses. These results constitute a breakthrough for the understanding of Khufu’s Pyramid and its internal structure. While there is currently no information about the role of this void, these findings show how modern particle physics can shed new light on the world’s archaeological heritage

Discovery of a big void in Khufu’s Pyramid by observation of cosmic-ray muons

The vertical sea-level muon spectrum at energies above 1 GeV and the muon intensities at depths up to 18 km w.e. in different rocks and in water are calculated. The results are particularly collated with a great body of the ground-level, underground, and underwater muon data. In the hadron-cascade calculations, we take into account the logarithmic growth with energy of inelastic cross sections and pion, kaon, and nucleon generation in pion-nucleus collisions. For evaluating the prompt-muon contribution to the muon flux, we apply the two phenomenological approaches to the charm production problem: the recombination quark-parton model and the quark-gluon string model. To solve the muon transport equation at large depths of a homogeneous medium, we used a semianalytical method, which allows the inclusion of an arbitrary ~decreasing! muon spectrum at the medium boundary and real energy dependence of both continuous and discrete muon energy losses. The method is checked for accuracy by direct Monte Carlo calculation. Whenever possible, we give simple fitting formulas describing our numerical results. @S0556-2821~98!00313-0# PACS number~s!: 13.85.Tp, 96.40.Tv

Atmospheric muon flux at sea level, underground and underwater

Atmospheric neutrino–fluxes are calculated over the wide energy range from 30 MeV to 3,000 GeV for the study of neutrino–physics using the data from underground neutrino–detectors. In this calculation, a full Monte Carlo method is employed for low energy neutrinos (30 MeV – 3 GeV), while a hybrid method is used for high energy neutrinos (1 – 3,000 GeV). At low energies, the ratio (�e+¯�e)/(�µ+¯�µ) agrees well with other calculations and is significantly different from observations. For the high energy neutrino–fluxes, the zenith angle dependence of atmospheric neutrino–flux is studied in detail, so that neutrino–oscillation parameters can be calculated for comparison with experimental results. The atmospheric muon–flux at high altitude and at sea level is studied to calibrate the neutrino–fluxes at low energies and high energies respectively. The agreement of our calculation with observations is satisfactory. The uncertainty of atmospheric neutrino–fluxes is also studied.

Calculation of the flux of atmospheric neutrinos

The spectrum of about 6 x 10/sup 5/ muons in the zenith angle range 0 = 68/sup 0/--82/sup 0/ and the energy range E = 1--1000 GeV has been measured by a Kiel-Desy collaboration at Hamburg. The data are represented by a simple form fit which goes as E/sup -2.57/sec 0 for the integral spectrum at very high energies. indicating that the galactic cosmic-ray nucleon spectrum is flatter than E/sup -2.75/ beyond 1000 GeV.

Cosmic-ray muon spectrum up to 1 TeV at 75° zenith angle

Cosmic ray muon spectra at sea-level up to 10 TeV

The absolute vertical muon intensity of cosmic rays at 1 GeV/c at sea level

The charge ratio fo cosmic-ray muons with energies up to 1 TeV in the zenith-angle range 68/sup 0/--82/sup 0/ has been measured. The data clearly show an enhancement of the charge ratio with increasing energy thus indicating a ''normal'' mass composition of galactic cosmic rays.

Sea-level muon charge ratio of cosmic rays at high energies

The absolute integral fluxes of cosmic ray muons above 0.35 GeV/c at sea levels are presented. The values are by 13% higher than the standard values quoted by Rossi in 1948.

H. Jokisch

Papers

Cosmic-ray muon spectrum up to 1 TeV at 75° zenith angle

Cosmic ray muon spectra at sea-level up to 10 TeV

The absolute vertical muon intensity of cosmic rays at 1 GeV/c at sea level

Sea-level muon charge ratio of cosmic rays at high energies

The absolute cosmic ray flux at sea level