594 research outputs found
Energy spectrum of cascades generated by muons in Baksan underground scintillation telescope
Spectrum of cascades generated by cosmic ray muons underground is presented. The mean zenith angle of the muon arrival is theta=35 deg the depth approx. 1000 hg/sq cm. In cascades energy range 700 GeV the measured spectrum is in agreement with the sea-level integral muon spectrum index gamma=3.0. Some decrease of this exponent has been found in the range 4000 Gev
Primary chemical composition from simultaneous recording of muons induced cascades and accompanying muon group underground
A new method to estimate the mean atomic number of primary cosmic rays in energy range 10 to the 3rd power to 10 to the 5th power Gev/nucleon is suggested. The Baksan underground scintillation telescope data are used for this analysis. The results of 7500 h run of this experiment are presented
Transversity and Transverse Spin in Nucleon Structure through SIDIS at Jefferson Lab
The JLab 12 GeV upgrade with a proposed solenoid detector and the CLAS12
detector can provide the granularity and three-dimensional kinematic coverage
in longitudinal and transverse momentum, , with to precisely measure the leading twist
chiral-odd and -odd quark distribution and fragmentation functions in SIDIS.
The large experimental reach of these detectors with a 12 GeV CEBAF at JLab
makes it {\em ideal} to obtain precise data on the {\em valence-dominated}
transversity distribution function and to access the tensor charge.Comment: 7 Pages, 2 figures. Summary of the working group on Transversity and
Transverse Spin Physics, from the workshop, "Inclusive and Semi-Inclusive
Spin Physics with High Luminosity and LargeAcceptance at 11 GeV", Thomas
Jefferson National Accelerator Facility (JLAB), December 13-14, 2006,
Jefferson Lab, Newport News, VA USA. Serves as input for the Nuclear Physics
Long Range Plan on QCD and Hadron Physic
TCRs with segment TRAV9-2 or a CDR3 histidine are overrepresented among nickel-specific CD4+ T cells
Background: Nickel is the most frequent cause of T cell-mediated allergic contact dermatitis worldwide. In vitro, CD4+ T cells from all donors respond to nickel but the involved αβ T cell receptor (TCR) repertoire has not been comprehensively analyzed. Methods: We introduce CD154 (CD40L) upregulation as a fast, unbiased, and quantitative method to detect nickel-specific CD4+ T cells ex vivo in blood of clinically characterized allergic and non allergic donors. Naïve (CCR7+ CD45RA+) and memory (not naïve) CD154+ CD4+ T cells were analyzed by flow cytometry after 5 hours of stimulation with 200 µmol/L NiSO4 ., TCR α- and β-chains of sorted nickel-specific and control cells were studied by high-throughput sequencing. Results: Stimulation of PBMCs with NiSO4 induced CD154 expression on ~0.1% (mean) of naïve and memory CD4+ T cells. In allergic donors with recent positive patch test, memory frequencies further increased ~13-fold and were associated with markers of in vivo activation. CD154 expression was TCR-mediated since single clones could be specifically restimulated. Among nickel-specific CD4+ T cells of allergic and non allergic donors, TCRs expressing the α-chain segment TRAV9-2 or a histidine in their α- or β-chain complementarity determining region 3 (CDR3) were highly overrepresented. Conclusions: Induced CD154 expression represents a reliable method to study nickel-specific CD4+ T cells. TCRs with particular features respond in all donors, while strongly increased blood frequencies indicate nickel allergy for some donors. Our approach may be extended to other contact allergens for the further development of diagnostic and predictive in vitro tests
Very-high energy gamma-ray astronomy: A 23-year success story in high-energy astroparticle physics
Very-high energy (VHE) gamma quanta contribute only a minuscule fraction -
below one per million - to the flux of cosmic rays. Nevertheless, being neutral
particles they are currently the best "messengers" of processes from the
relativistic/ultra-relativistic Universe because they can be extrapolated back
to their origin. The window of VHE gamma rays was opened only in 1989 by the
Whipple collaboration, reporting the observation of TeV gamma rays from the
Crab nebula. After a slow start, this new field of research is now rapidly
expanding with the discovery of more than 150 VHE gamma-ray emitting sources.
Progress is intimately related with the steady improvement of detectors and
rapidly increasing computing power. We give an overview of the early attempts
before and around 1989 and the progress after the pioneering work of the
Whipple collaboration. The main focus of this article is on the development of
experimental techniques for Earth-bound gamma-ray detectors; consequently, more
emphasis is given to those experiments that made an initial breakthrough rather
than to the successors which often had and have a similar (sometimes even
higher) scientific output as the pioneering experiments. The considered energy
threshold is about 30 GeV. At lower energies, observations can presently only
be performed with balloon or satellite-borne detectors. Irrespective of the
stormy experimental progress, the success story could not have been called a
success story without a broad scientific output. Therefore we conclude this
article with a summary of the scientific rationales and main results achieved
over the last two decades.Comment: 45 pages, 38 figures, review prepared for EPJ-H special issue "Cosmic
rays, gamma rays and neutrinos: A survey of 100 years of research
Nuclear transparency and effective kaon-nucleon cross section from the A(e, e'K+) reaction
We have determined the transparency of the nuclear medium to kaons from
measurements on C, Cu, and Au targets.
The measurements were performed at the Jefferson Laboratory and span a range in
four-momentum-transfer squared Q=1.1 -- 3.0 GeV. The nuclear
transparency was defined as the ratio of measured kaon electroproduction cross
sections with respect to deuterium, (). We further
extracted the atomic number () dependence of the transparency as
parametrized by and, within a simple model assumption,
the in-medium effective kaon-nucleon cross sections. The effective cross
sections extracted from the electroproduction data are found to be smaller than
the free cross sections determined from kaon-nucleon scattering experiments,
and the parameter was found to be significantly larger than those
obtained from kaon-nucleus scattering. We have included similar comparisons
between pion- and proton-nucleon effective cross sections as determined from
electron scattering experiments, and pion-nucleus and proton-nucleus scattering
data.Comment: 7 pages, 5 figure
Study of the A(e,e') Reaction on H, H, C, Al, Cu and Au
Cross sections for the p()n process on H, H, C,
Al, Cu and Au targets were measured at the Thomas
Jefferson National Accelerator Facility (Jefferson Lab) in order to extract the
nuclear transparencies. Data were taken for four-momentum transfers ranging
from =1.1 to 4.8 GeV for a fixed center of mass energy of =2.14
GeV. The ratio of and was extracted from the measured
cross sections for H, H, C and Cu targets at = 2.15
and 4.0 GeV allowing for additional studies of the reaction mechanism. The
experimental setup and the analysis of the data are described in detail
including systematic studies needed to obtain the results. The results for the
nuclear transparency and the differential cross sections as a function of the
pion momentum at the different values of are presented. Global features
of the data are discussed and the data are compared with the results of model
calculations for the p()n reaction from nuclear targets.Comment: 28 pages, 19 figures, submited to PR
Measurement of the 3He(e,e'p)pn reaction at high missing energies and momenta
Results of the Jefferson Lab Hall A quasielastic 3He(e,e'p)pn measurements
are presented. These measurements were performed at fixed transferred momentum
and energy, q = 1502 MeV/c and omega = 840 MeV, respectively, for missing
momenta p_m up to 1 GeV/c and missing energies in the continuum region, up to
pion threshold; this kinematic coverage is much more extensive than that of any
previous experiment. The cross section data are presented along with the
effective momentum density distribution and compared to theoretical models.Comment: 5 pages, 3 figures, updated to reflect published paper: minor text
changes from previous version along with updated and added reference
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