Using the effective potential approach for composite operators, we have formulated a general method of calculation of the truly non-perturbative Yang-Mills vacuum energy density (this is, by ...definition, the bag constant apart from the sign). It is the main dynamical characteristic of the QCD ground state. Our method allows one to make it free of the perturbative contributions ('contaminations'), by construction. We also perform an actual numerical calculation of the bag constant for the confining effective charge. Its choice uniquely defines the bag constant, which becomes free of all types of perturbative contributions now, as well as possessing many other desirable properties such as colorless, gauge independence, etc. Using the trace anomaly relation further, we develop a general formalism which makes it possible to relate the bag constant to the gluon condensate not using the weak coupling solution for the corresponding beta function. Our numerical result for the bag constant shows good agreement with other phenomenological estimates of the gluon condensate.
A small-size prototype of a new Ring Imaging Cherenkov (RICH) detector using for the first time pressurized C4F8O radiator gas and a photon detector consisting of MWPC equipped with a CsI ...photocathode has been built and tested at the PS accelerator at CERN. It contained all the functional elements of the detector proposed as Very High Momentum Particle Identification (VHMPID) upgrade for the ALICE experiment at LHC to provide charged hadron track-by-track identification in the momentum range starting from 5 potentially up to 25GeV/c. In the paper the equipment and its elements are described and some characteristic test results are shown.
Predictions for cold nuclear matter effects on charged hadrons, identified light hadrons, quarkonium and heavy flavor hadrons, Drell–Yan dileptons, jets, photons, gauge bosons and top quark pairs ...produced in p+Pb collisions at sNN=8.16 TeV are compiled and, where possible, compared to each other. Predictions of the normalized ratios of p+Pb to p+p cross sections are also presented for most of the observables, providing new insights into the expected role of cold nuclear matter effects. In particular, the role of nuclear parton distribution functions on particle production can now be probed over a wider range of phase space than ever before.
We investigate the usage of a schlieren imaging setup to measure the geometrical dimensions of a plasma channel in atomic vapor. Near resonant probe light is used to image the plasma channel in the ...tenuous vapor and machine learning techniques are tested for extracting quantitative information from the images. We build a database of simulated signals with a range of plasma parameters for training Deep Neural Networks, and demonstrate that they can estimate, from the schlieren images, reliably and with high accuracy the location, the radius and the maximum ionization fraction of the plasma channel as well as the width of the transition region between the core of the plasma channel and the unionized vapor. We test several different neural network architectures with supervised learning and show that the parameter estimations supplied by the networks are resilient with respect to slight changes of the experimental parameters that may occur in the course of a measurement.
•Machine learning programs can evaluate images provided by a laser probe.•The parameters of a plasma channel can be estimated quickly and accurately.•Parameter estimation works well for measurements taken under varying circumstances.
We report on the R&D results for a Very High Momentum Particle Identification (VHMPID) detector, which was proposed to extend the charged hadron track-by-track identification in the momentum range ...from 5 to 25 GeV/c in the ALICE experiment at CERN. It is a RICH detector with focusing geometry using pressurized perfluorobutane (C sub(4)F sub(8)O) as a Cherenkov radiator. A MWPC with a CsI photocathode was investigated as the baseline option for the photon detector. The results of beam tests performed on RICH prototypes using both liquid C sub(6)F sub(14) radiator (in proximity focusing geometry for reference measurements) and pressurized C sub(4)F sub(8)O gaseous radiator will be shown in this paper. In addition, we present studies of a CsI based gaseous photon detector equipped with a MWPC having an adjustable anode-cathode gap, aiming at the optimization of the chamber layout and performance in the detection of single photoelectrons.
The measurement of the production of charm jets, identified by the presence of a D$^{0}$ meson in the jet constituents, is presented in proton–proton collisions at centre-of-mass energies of $ ...\sqrt{s} $ = 5.02 and 13 TeV with the ALICE detector at the CERN LHC. The D$^{0}$ mesons were reconstructed from their hadronic decay D$^{0}$ → K$^{−}$π$^{+}$ and the respective charge conjugate. Jets were reconstructed from D$^{0}$-meson candidates and charged particles using the anti-k$_{T}$ algorithm, in the jet transverse momentum range 5 < p$_{T,chjet}$< 50 GeV/c, pseudorapidity |η$_{jet}$| < 0.9 − R, and with the jet resolution parameters R = 0.2, 0.4, 0.6. The distribution of the jet momentum fraction carried by a D$^{0}$ meson along the jet axis $ \left({z}_{\Big\Vert}^{\textrm{ch}}\right) $ was measured in the range 0.4 <$ {z}_{\Big\Vert}^{\textrm{ch}} $< 1.0 in four ranges of the jet transverse momentum. Comparisons of results for different collision energies and jet resolution parameters are also presented. The measurements are compared to predictions from Monte Carlo event generators based on leading-order and next-to-leading-order perturbative quantum chromodynamics calculations. A generally good description of the main features of the data is obtained in spite of a few discrepancies at low p$_{T,chjet}$. Measurements were also done for R = 0.3 at $ \sqrt{s} $ = 5.02 and are shown along with their comparisons to theoretical predictions in an appendix to this paper.graphic not available: see fulltext
We investigated recent observation data of pulsar masses of PSR J0740+6620, PSR J0348+0432, and PSR J1614−2230 based on the extended
σ
-
ω
model. We assumed that these pulsars are maximal mass ...compact star, which suggest that the core approximation can be applied. Using the linear relations between the microscopic and macroscopic parameters of neutron stars suggested by this model, we estimated the values of the nucleon Landau mass and nuclear compressibility
m
L
=776.0
−84.9
+38.5
MeV and
K
=242.7
−28.0
+57.2
MeV, respectively.
The first measurement of the production of pions, kaons, (anti-)protons and ϕ mesons at midrapidity in Xe–Xe collisions at $\sqrt{s_{NN}}$ = 5.44 TeV is presented. Transverse momentum ...(pT) spectra and pT-integrated yields are extracted in several centrality intervals bridging from p–Pb to mid-central Pb–Pb collisions in terms of final-state multiplicity. The study of Xe–Xe and Pb–Pb collisions allows systems at similar charged-particle multiplicities but with different initial geometrical eccentricities to be investigated. A detailed comparison of the spectral shapes in the two systems reveals an opposite behaviour for radial and elliptic flow. In particular, this study shows that the radial flow does not depend on the colliding system when compared at similar charged-particle multiplicity. In terms of hadron chemistry, the previously observed smooth evolution of particle ratios with multiplicity from small to large collision systems is also found to hold in Xe–Xe. In addition, our results confirm that two remarkable features of particle production at LHC energies are also valid in the collision of medium-sized nuclei: the lower proton-to-pion ratio with respect to the thermal model expectations and the increase of the ϕ-to-pion ratio with increasing final-state multiplicity.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
29.
Portable cosmic muon telescope for environmental applications Barnaföldi, Gergely Gábor; Hamar, Gergő; Melegh, Hunor Gergely ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2012, Letnik:
689
Journal Article
Recenzirano
A portable, low power consumption cosmic muon tracking system based on Close Cathode MWPC technology is presented, which is designed for operation in highly humid environmental conditions such as ...underground caves, tunnels, or cellars. The system measures the angular distribution of cosmic muons with resolution of 10mrad, allowing for a tomographic mapping of the soil density above the detector unit. The size of the detector, 0.1m2 of total sensitive surface, was designed to fulfill the requirement of transport through humanly passable natural cave tunnels. First results from the Ariadne Cave System in Pilis Mountains, Hungary are shown, which constrains the necessary data taking time for meaningful tomographic mapping.
► Cosmic muon tracking system for underground applications presented. ► Operation in highly humid environment of natural caves demonstrated. ► Tomographic mapping at 60m depth was performed during 50 days in Pilis Mountains, Hungary.
Quantum Chromodynamics (QCD) is the most up-to-date theory of the strong interaction. Its predictions have been verified experimentally, and it is a cornerstone of the Standard Model of particle ...physics. However, standard perturbative procedures fail if applied to low-energy QCD. Even the discovery of the Higgs Boson will not solve the problem of masses originating from the non-perturbative behavior of QCD. This book presents a new method, the introduction of the ‘mass gap’, first suggested by Arthur Jaffe and Edward Witten at the turn of the millennium. It attempts to show that, to explain the mass-spectrum of QCD, one needs the mass scale parameter (the mass gap) instead of other massive particles. The energy difference between the lowest order and the vacuum state in Yang–Mills quantum field theory, the mass gap is in principle responsible for the large-scale structure of the QCD ground state, and thus also for its non-perturbative phenomena at low energies. This book not only presents the mass gap, but also details the applications and outlook of the mass gap method. A detailed summary of references and problems are included as well.
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