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1.
Twenty high energy nuclear interactions produced in the graphite units of an emulsion chamber were recorded. The emulsion
chamber was exposed to cosmic rays at an atmospheric depth of 10 g cm−2 for about 7 hr over Hyderabad, India. Fourteen interactions which radiated energyΣ E
r⩾1000 GeV in the form ofγ-rays were analysed in detail. The median energy 〈Σ E
r〉 of the interactions was 1600 GeV. Results concerning the multiplicity, the transverse and longitudinal momentum distributions,
and the fractional energy distribution ofγ-rays in these interactions are presented. The average transverse momentum ofπ
0—mesons <pt
π
0> is found to increase very slowly with the primary energyE
0 and it can be approximated by the function <pt
π
0>=0·238E
0
0.06
. 相似文献
2.
An emulsion chamber was used to study the characteristics of high energy nuclear interactions from the production spectra
ofγ-rays. The emulsion chamber, which comprised of two parts, namely the detector and the graphite producer unit, was exposed
to cosmic rays for about 7 hr at an atmospheric depth of 10 g cm−2 at Hyderabad (geomagnetic latitude 7·6°N). 720 electromagnetic cascades due toγ-rays were recorded in the detector. These cascades were classified into three groups; (a)γ-rays from nuclear interactions in the detector (b)γ-rays from nuclear interactions in the producer unit and (c)γ-rays of atmospheric origin. The energies of the cascades were determined using photometric method. The spectra ofγ-rays from groups (a) and (c) were determined and compared with similar spectra obtained at greater atmospheric depths. The
spectra were found to obey a power law. The spectrum ofγ-rays of atmospheric origin was found to steepen at high energies,E
r>2200 GeV. 相似文献
3.
A study of 100 interactions, produced by secondary particles from 200 GeV/c proton interactions in nuclear emulsions, has
been made to estimate the transverse momenta of the secondary particles. The data have been analysed by different methods
of energy estimation and the weighted average values ofp
t
have been compared as estimated from various methods. An average value ofp
t
equal to 0.38 ± 0.03 GeV/c, in proton-nucleus interactions at 200 GeV/c, has been obtained from the production mechanism
method. 相似文献
4.
M. Aglietta B. Alessandro P. Antonioli F. Arneodo L. Bergamasco A. Campos Fauth C. Castagnoli A. Castellina C. Cattadori A. Chiavassa et al. 《Il Nuovo Cimento C》1992,15(4):441-446
Summary A search for cosmic gamma-ray bursts in the GeV energy range has been performed by means of the EAS-TOP Extensive Air Shower
array at Campo Imperatore (Gran Sasso Laboratories) during the period March–December 1990. In 2566.5 hours of measurement
the obtained upper limit to the rate of bursts of amplitude >2% of the cosmic-ray intensity and time duration τ=1 s, isR≤7.9y−1 (90% c.l.). Assuming for γ-rays a differential energy spectrumS(E
0
)≈E
0
−2.5
, the corresponding upper limit to the energy flux of γ-rays with energy >5 GeV in bursts of duration τ≤1 s is Φ<8.3·10−5erg cm−2. 相似文献
5.
《The European Physical Journal A - Hadrons and Nuclei》2008,35(3):333-342
The exclusive reactions γp → K
*0Σ+(1189) and γp → K
0π0Σ+(1189) , leading to the p 4π0 final state, have been measured with a tagged photon beam for incident energies from threshold up to 2.5GeV. The experiment
has been performed at the tagged photon facility of the ELSA accelerator (Bonn). The Crystal Barrel and TAPS detectors were
combined to a photon detector system of almost 4π geometrical acceptance. Differential and total cross-sections are reported.
At energies close to the threshold, a flat angular distribution has been observed for the reaction γp → K
0π0Σ+ suggesting dominant s -channel production. Σ*(1385) and higher-lying hyperon states have been observed. An enhancement in the forward direction in the angular distributions
of the reaction γp → K
*0Σ+ indicates a t -channel exchange contribution to the reaction mechanism. The experimental data are in reasonable agreement with recent theoretical
predictions. 相似文献
6.
S. M. Kiselev 《Physics of Atomic Nuclei》2009,72(3):517-521
Using the extrapolation of existing data, estimations of prompt-photon production at FAIR energies have been made. At y = y
c.m. the rapidity density of prompt photons with p
t
> 1.5 GeV/c per central Au + Au event at 25 A GeV is estimated as ∼10−4. With the planned beam intensity 109 per second and 1% interaction probability, for 10% of most central events one can expect the prompt-photon rate ∼102 photons per second. Direct photons from the hadron scenario of ion collisions generated by the Hadron-String-Dynamics (HSD)
transport approach with implemented meson scatterings πρ → πγ, ππ → ργ have been analyzed. Photons from short-living resonances (e.g., ω → π
0
γ) decaying during the dense phase of the collision should be considered as direct photons. They contribute significantly in
the directphoton spectrum at p
t
= 0.5–1 GeV/c. At the FAIR energy 25 A GeV in Au + Au central collisions the HSD generator predicts, as a lower estimate, γ
direct/ ≃ 0.5% in the region p
t
= 0.5–1 GeV/c. At p
t
= 1.5–2 GeV/c γ
prompt/ ≃ 2%. Thermal direct photons have been evaluated with the Bjorken Hydro-Dynamics (BHD) model. The BHD spectra differ strongly
from the HSD predictions. The direct-photon spectrumis very sensitive to the initial temperature parameter T
0 of the model. The 10-MeV increase in the T
0 value leads to ∼2 times higher photon yield.
The text was submitted by the authors in English. 相似文献
7.
Cross-sections, beam asymmetries, and recoil polarisations for the reactions γp → K
+Λ;γp → K
+Σ0, and γp → K
0Σ+ have been measured by the SAPHIR, CLAS, and LEPS Collaborations with high statistics and good angular coverage for centre-of-mass
energies between 1.6 and 2.3 GeV. The combined analysis of these data with data from π and η photoproduction reveals evidence
for new baryon resonances in this energy region. A new P11 state with mass 1840 MeV and width 140 MeV was observed contributing to most of the fitted reactions. The data demand the
presence of two D13 states at 1875 and, optimistically, at 2170 MeV. 相似文献
8.
Sayipjamal Dulat Bing-Song Zou 《The European Physical Journal A - Hadrons and Nuclei》2005,26(1):125-134
With accumulation of high statistics data at BES and CLEO-c, many new interesting channels can get enough statistics for partial-wave
analysis (PWA). Among them, ψ↦γpˉ,γΛˉ,γΣˉ,γΞˉ channels provide a good place for studying baryon-antibaryon interactions; the double radiative decays ψ↦γγV with V ≡ ρ,ω,φ have a potential to provide information on the flavor content of any meson resonances (R) with positive charge parity
(C = +) and mass above 1 GeV through ψ↦γR↦γγV; ψ(2s)↦γχc0,1,2 with χc0,1,2↦Kˉπ+π- and 2π+2π- decays are good processes to study χcJ charmonium decays. Using the covariant tensor formalism, here we provide theoretical PWA formulae for these channels. 相似文献
9.
β-γ-γ directional correlation studies for the cascades (i)β-rays ofE
max=0.12 MeV,γ-rays of 557 keV andγ-rays of 53 keV and (ii)β-rays ofE
max=0.21 MeV,γ-rays of 444 keV andγ-rays of 53 keV have been made. The triple correlation functionsW(θ) were obtained to beW(θ)=1+(−0.153±0.031)P
2(cosθ)+(0.004±0.035)P
4(cosθ) forβ-rays ofE
max 0.12 MeV→557→53 keV cascade andW(θ)=1+(0.163±0.042)P
2(cosθ)+(−0.035±0.058)P
4(cosθ) forβ rays ofE
max=0.21 MeV→444 keV→53 keV cascade.
Spins and parities of the 650, 537 and 93 keV levels of103Rh are deduced by triple angular correlation and the internal conversion coefficient studies. Multipolarities of the transitions
are also determined. 相似文献
10.
W. Cassing Ye.S. Golubeva L.A. Kondratyuk 《The European Physical Journal A - Hadrons and Nuclei》2000,7(2):279-285
We study the possibility to measure the elastic ΦN (Φ≡J/ψ,ψ(2S), ψ(3770), χ2c) scattering cross section in the reaction ˉp+d→Φ+n
sp and the elastic D(ˉD)N scattering cross section in the reaction ˉp+d→D
−
D
0
p
sp. Our studies indicate that the elastic scattering cross sections can be determined for Φ momenta about 4–6 GeV/c and D/ˉD momenta 2–5 GeV/c by selecting events with p
t≥ 0.4 GeV/c for Φ's and p
t(p
sp) ≥ 0.5 GeV/c for D/ˉD-meson production.
Received: 8 November 1999 相似文献
11.
N. M. Agababyan V. V. Ammosov M. Atayan N. Grigoryan H. Gulkanyan A. A. Ivanilov Zh. Karamyan V. A. Korotkov 《Physics of Atomic Nuclei》2007,70(10):1739-1742
Using the data obtained with the SKAT bubble chamber, the total yields of K*(892)+, Σ+(1385), and Σ0 are estimated for the first time in neutrino-induced reactions at moderate energy 〈E
v〉 = 10.4 GeV. It is shown that the recently observed enhancement of the K
0 and Λ yields in vA interactions as compared to vN interactions is contributed only slightly by the K*(892)+ and Σ+(1385) production. The contribution of resonances to the K
0 and Λ yields is found to be in qualitative agreement with higher energy (〈E
v〉 ≳ 40 GeV) data. It is shown that the energy dependence of the K*(892)+ mean multiplicity in vN interactions is approximately linear in the range of 〈E
v〉 ≈ 10−60 GeV, while that for Σ0 in vA interactions (A = 20−21) is approximately logarithmic in the range of 〈E
v〉 ≈ = 10−150 GeV.
The text was submitted by the authors in English. 相似文献
12.
《The European Physical Journal C - Particles and Fields》2008,57(3):499-514
Muon bremsstrahlung photons converted in front of the DELPHI main tracker (TPC) in dimuon events at LEP1 were studied in two
photon kinematic ranges: 0.2<E
γ
≤1 GeV and transverse momentum with respect to the parent muon p
T
<40 MeV/c, and 1<E
γ
≤10 GeV and p
T
<80 MeV/c. A good agreement of the observed photon rate with predictions from QED for the muon inner bremsstrahlung was found, contrary
to the anomalous soft photon excess that has been observed recently in hadronic Z
0 decays. The obtained ratios of the observed signal to the predicted level of the muon bremsstrahlung are 1.06±0.12±0.07 in
the photon energy range 0.2<E
γ
≤1 GeV and 1.04±0.09±0.12 in the photon energy range 1<E
γ
≤10 GeV. The bremsstrahlung dead cone is observed for the first time in the direct photon production at LEP.
Deceased. 相似文献
13.
H. -W. Siebert 《The European physical journal. Special topics》2008,162(1):147-153
The large amount of data on hyperon polarizations in inclusive production by hadrons at high energies has recently been extended
to Λ and Ξ
− production by Σ
− beams. The sign of the Ξ
− polarization is negative and the same as in Λ and Ξ
− production by protons. The sign of the Λ polarization, however, is positive, in contrast to the negative sign expected by analogy to the proton beam data for Λ and Ξ
− polarization. Theoretical expectations, for instance from a recombination model, also favoured negative polarization of Λ produced by Σ
−. Moreover, while the Λ polarization increases with p
t
at values below ≈1 GeV/c as observed for other hyperon polarizations, it vanishes above p
t
≈ 1.2 GeV/c. Such a breakdown at large pt has not been observed in any other beam/hyperon combination. 相似文献
14.
A. Sibirtsev J. Haidenbauer H. -W. Hammer U. -G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》2007,32(2):229-241
We utilize existing inclusive data on K+-meson momentum spectra of the reaction pp→K
+
X at T
p = 2.3-2.85GeV to deduce total cross-sections for pp→K
+
Σ
+
n. The method used to extract those cross-sections is explained and discussed in detail. Our result for T
p = 2.85GeV is consistent with the data point from a direct measurement at the same beam energy. The cross-section obtained
for T
p = 2.3GeV is with 13.7±2.3μb considerably smaller than the value found in a recent experiment by the COSY-11 Collaboration
at a somewhat lower beam energy, indicating that the pp→K
+
Σ
+
n reaction cross-section could exhibit a rather unusual energy dependence. 相似文献
15.
A. K. Managadze V. I. Osedlo T. M. Roganova L. G. Sveshnikova V. I. Galkin I. V. Rakobolskaya L. A. Goncharova K. A. Kotelnikov N. G. Polukhina 《Physics of Atomic Nuclei》2007,70(1):184-190
A gamma-hadron superfamily of cosmic-rays created by a primary cosmic-ray particle with energy above 1016 eV was detected at an altitude of 30 km by a stratospheric balloon-borne emulsion chamber. Being of superhigh energy, this
event is the unique example in the world statistics of practically pure nuclear interactions in the energy range unattainable
for modern accelerators. The present analysis allowed one to estimate the interaction height above the chamber and transverse
momenta of the secondaries produced in the interaction. The mean value of transverse momenta appears to be very large (〈p
t〉 > 2.5 GeV/c).
The text was submitted by the authors in English. 相似文献
16.
The lowest momentum at which the total scattering cross-section data are available for Σ+
p and Σ−
p scattering is 145 MeV/c and 142.5 MeV/c respectively. Thus extracting low energy parameters amounts to extrapolating the
data to still lower energies. Using the analytic structure of foward scattering amplitude to advantage a parameterization
of theσ
T
is presented which is hoped to be more reliable and stable for deriving results through extrapolation. The scattering lengths
and effective ranges for the Σ+
p and Σ−
p are also estimated. 相似文献
17.
H.W. Dannhausen E.J. Durwen H.M. Fischer M. Leneke W. Niehaus F. Takasaki 《The European Physical Journal A - Hadrons and Nuclei》2001,11(4):441-455
The differential cross-section for the reaction γp↦π +
n was measured using the bremsstrahlung beam of the Bonn 2.5 GeV electron synchrotron. The pions were detected and momentum
analysed in a multichannel magnet spectrometer. Data reduction resulted in 1278 measured cross-sections which are presented
as energy distributions at six laboratory angles between 180° and 95°. The range of laboratory photon energies extended from
0.3 to 2.1 GeV. The statistical accuracy is better than 3 percent, the systematic error is about 5 percent. The data are compared
with other experimental results and predictions of a phenomenological analysis. These cross-sections are the result of a measurement
program which was started in the seventies. Further results will be reported in forthcoming publications.
Received: 2 February 2000 / Accepted: 14 August 2001 相似文献
18.
A telescope of area 4 m2, consisting of horizontal layers of plastic scintillators, neon flash tubes and absorbers was operated at a depth of 754
hg/cm2 in the Kolar Gold Mines. New values for the vertical intensities of muons have been obtained from observations of the angular
distribution over the slant depths ∼ 750–2300 hg/cm2 and are compared with the existing measurements. From the angular distribution observed, we conclude that muons are produced
wholly through the decay of pions and kaons up to energies of the order of 1 TeV. A value of 0.3±0.2 is estimated for theK/π ratio at production, for muon energies around 500 GeV. A decoherence distribution has been obtained for parallel muon events
up to distances of the order of 10 m. From this we conclude that the averageP
t of the parents of muons of energy ∼ 250 GeV is of the order of 0.3 GeV/c. From an analysis of rock showers, we obtain the
cross section for inelastic interaction of muons of mean energy 100 GeV as (3.8±1.5)×10−30 cm2/nucleon. 相似文献
19.
The upgraded Tevatron collider, with an expected integrated luminosity of 100 pb−1, shall push up the top quark discovery limit from 80 to 200 GeV. The distinctive signature of the signal vis-a-vis background
are analysed for this mass range of top.
The ratio ofW andZ widths, measured indirectly by the UA1 and UA2 experiments, has been shown to favourm
t
<60 GeV [8]. But the experimental errors are too large to derive any meaningful upper bound form
t
[2] 相似文献
20.
The H Collaboration 《The European Physical Journal C - Particles and Fields》2006,46(3):585-603
Cross sections for elastic production of J/ψ mesons in photoproduction and electroproduction are measured in electron proton
collisions at HERA using an integrated luminosity of 55 pb-1. Results are presented for photon virtualities Q2 up to 80 GeV2. The dependence on the photon-proton centre of mass energy Wγp is analysed in the range 40≤Wγp≤305 GeV in photoproduction and 40≤Wγp≤160 GeV in electroproduction. The Wγp dependences of the cross sections do not change significantly with Q2 and can be described by models based on perturbative QCD. Within such models, the data show a high sensitivity to the gluon
density of the proton in the domain of low Bjorken x and low Q2. Differential cross sections dσ/dt, where t is the squared four-momentum transfer at the proton vertex, are measured in the
range |t|<1.2 GeV2 as functions of Wγp and Q2. Effective Pomeron trajectories are determined for photoproduction and electroproduction. The J/ψ production and decay angular
distributions are consistent with s-channel helicity conservation. The ratio of the cross sections for longitudinally and
transversely polarised photons is measured as a function of Q2 and is found to be described by perturbative QCD based models. 相似文献