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arXiv2013

Performance test of wavelength-shifting acrylic plastic Cherenkov detector

The collection efficiency for Cherenkov light incident on a wavelength shifting plate (WLS) has been determined during a beam test at the Proton Synchrotron facility located in the National Laboratory for High Energy Physics (KEK), Tsukuba, Japan. The experiment was conducted in order to determine the detector's response to photoelectrons converted from photons produced by a fused silica radiator; this allows for an approximation of the detector's quality. The yield of the photoelectrons produced through internally generated Cherenkov light as well as light incident from the radiator was measured as a function of the momentum of the incident hadron beam. The yield is proportional to sin$^2$$θ_c$, where $θ_{c}$ is the opening angle of the Cherenkov light created. Based on estimations and results from similarly conducted tests, where the collection efficiency was roughly 39%, the experimental result was expected to be around 40% for internally produced light from the WLS. The results of the experiment determined the photon collection response efficiency of the WLS to be roughly 62% for photons created in a fused silica radiator and 41% for light created in the WLS.

nucl-ex↗

arXiv2011

Even-odd effect in multifragmentation products: the footprints of evaporation

The analysis of experimental production cross-sections of intermediate-mass fragments (IMF) of several nuclear reactions at relativistic energy, measured at the FRS, GSI Darmstadt, revealed a very strong and complex even-odd staggering. The origin of this effect is related to the condensation process of hot nuclei while cooling down by evaporation. The characteristics of the staggering correlate strongly with the lowest particle separation energy of the final experimentally observed nuclei, but not with the binding energy. The study confirms the important role of the de-excitation process in multifragmentation reactions, and indicates that sequential decay strongly influences the yields of IMF, which are often used to extract information on the nature of nuclear reactions at high energies.

nucl-ex↗

arXiv2010

Measurement of the dielectron continuum in p+p and Au+Au collisions at RHIC

PHENIX has measured the e^+e^- pair continuum in sqrt(s_NN) = 200 GeV Au+Au and p+p collisions over a wide range of mass and transverse momenta. While the p+p data in the mass range below the phi meson are well described by known contributions from light meson decays, the Au+Au minimum bias inclusive mass spectrum shows an enhancement by a factor of 4.7 +/- 0.4(stat)} +/- 1.5(syst) +/- 0.9(model) in the mass range 0.15<m_ee<0.75 GeV/c^2. At low mass (m_ee<0.3 GeV/c^2) and high p_T (1<p_T<5~GeV/c) an enhanced e^+e^- pair yield is observed that is in qualitative agreement with hydrodynamical models of thermal photon emission with initial temperatures ranging from T_init ~= 300-600 MeV at times of 0.6-0.15 fm/c after the collision.

nucl-ex↗

arXiv2010

Study of the eta-prime meson structure, width and interactions with nucleons at COSY-11

We present results on the isospin dependence of the eta-prime production cross section in nucleon-nucleon collisions, as well as the results of comparative analysis of the invariant mass distributions for the pp-->pp eta-prime and pp-->pp eta reactions in the context of the proton-eta and proton-eta-prime interaction. Additionally, the value of the total width of the eta-prime is reported as derived directly from the measurement of the mass distribution and an explanation of the experimental technique used in order to achieve a precision about an order of magnitude better then former experiments is included.

nucl-ex↗

arXiv2010

Inference of weak nuclear collectivity from atomic masses

I explore weakly-collective singly-closed shell nuclei with high-j shells where active valence neutrons and particle-particle correlations may be the dominant collective degree of freedom. The combination of large and close-lying proton and neutron pairing gaps extracted from experimental masses seems to charaterize the origin of the weak collectivity observed in Ni and Sn superfluids with $N\approx Z$. The trend of $E2$ transition strengths, i.e., $B(E2; 2^+_1\rightarrow 0^+_1)$ values, in these nuclei is predicted from proton and neutron pairing-gap information. The agreement with the Ni isotopes is excellent and recent experimental results support the trend in the Sn isotopes. This work emphasizes the importance of atomic masses in elucidating nuclear-structure properties. In particular, it indicates that many-body microscopic properties such as nuclear collectivity could be directly inferred from more macroscopic average properties such as atomic masses.

nucl-th↗

arXiv2011

Search for long-range forces of a neutron and atoms with a trap of ultracold neutrons

A method of using a gravitational UCN spectrometer to search for long-range forces between neutrons and atoms is proposed. The constraints on the strength of long-range forces within the range of 10-10 - 10-4 cm can be obtained from the experiments on measurements of the total cross section of interaction of UCN with atoms of the noble gases (He, Ne, Ar, Kr) and the data on the coherent neutron scattering length of the nucleus. The first result of such an analysis is presented. Further prospect of UCN method is discussed.

nucl-ex↗

arXiv2010

Physics with Nuclei at an Electron Ion Collider

Lepto-nuclear colliders offer unique experimental opportunities to probe QCD in an extended medium. Of the many possibilities, three experiments are described here that are clearly feasible and of high scientific importance. First, a direct measurement of the saturation scale is possible using the broadening of the transverse momentum distribution of hadrons produced in semi-inclusive DIS. This connection to saturation physics will provide a quantitative measure of the degree to which this fundamental QCD phenomenon is occurring, and has important consequences in other high-energy scattering studies. Second, the measurement of quark energy loss is feasible, either as a direct measurement at a lower-energy EIC, or as an indirect measurement using hadron attenuation at higher energies. Such a measurement will offer the first experimental validation of the energy independence of this process, which is a consequence of the QCD analog of the LPM effect in QED. The third experiment is to determine the mechanisms of hadronization using the nucleus as a spatial analyzer, intercomparing hadron attenuation for nuclei of a range of sizes. The extended reach of the EIC in energy will allow probes of these mechanisms in the crucial high-z region for the heaviest nuclei, and will permit study of hadronization in heavy quark meson and baryon systems.

nucl-ex↗

arXiv2010

eta meson production in nucleon-nucleon collisions

New experimental data are presented on the energy dependence of the total cross sections for the np -> d eta and quasi-two-body pp -> pp eta reactions, where the final diproton is detected at very low excitation energy. Differential cross sections of pp -> pp eta away from threshold show the influence of higher partial waves and a partial wave decomposition is attempted.

nucl-th↗

arXiv2010

Critical examination of RHIC paradigms-mostly high pT

A critical examination of RHIC paradigms is presented. Topics include: search for a critical point with a low energy scan; the lack of understanding of radiative processes in a medium in QCD compared in detail to examples from QED; the reason why some physicists started to measure particles at large pT in the 1960's; a review of the discovery of hard-scattering in p-p collisions in the 1970's via single-inclusive and two-particle correlations and application of these techniques at RHIC. Several paradigms in both soft and hard physics which are popular at RHIC are discussed and challenged.

nucl-ex↗

arXiv2010

Elliptic flow of heavy flavors

The propagation of charm and bottom quarks through an ellipsoidal domain of quark gluon plasma has been studied within the ambit of non-equilibrium statistical mechanics. Energy dissipation of heavy quarks by both radiative and collisional processes are taken in to account. The experimental data on the elliptic flow of the non-photonic electrons resulting from the semi-leptonic decays of hadrons containing heavy flavours has been reproduced with the same formalism that has been used earlier to reproduce the nuclear suppression factors. The elliptic flow of the non-photonic electron from heavy meson decays produced in nuclear collisions at LHC and low energy RHIC run have also been predicted.

nucl-th↗

arXiv2010

Studies of properties of the eta-prime meson at the COSY-11 facility

We shortly discuss results on the isospin dependence of the eta-prime production cross section in nucleon-nucleon collisions, results of comparative analysis of the invariant mass distributions for the pp-->pp eta-prime and pp-->pp eta reactions, and we present the value of the total width of the eta-prime meson as derived directly from the mass distribution measured with the mass resolution of 0.3 MeV/c^2.

nucl-ex↗

arXiv2010

High-pT paradigms revisited

We present an attempt at a critical overview of the current status of modeling for high-pT processes in nuclei. The paper covers several topics including coherence phenomena, in particular gluon shadowing and CGC; nuclear effects related to the restrictions imposed by energy conservation at large xL and xT ; space-time development of hadronization of highly virtual light and heavy partons and the related time scales; and the role of early production and subsequent attenuation of pre-hadrons in a dense medium. We identify several intriguing problems in the current paradigms for high-pT processes and propose solutions for some of them.

hep-ph↗

arXiv2010

Scintillation properties of ceramics based on zinc oxide

Ceramics ZnO:Zn of 20mm diameter and 1.6mm thickness with an optical transparency up to 0.33 in the visible region have been prepared by hot pressing technique. Scintillating and luminescent characteristics such as emission spectra, decay time, yield, and TSL glow curve have been measured under X-ray excitation. Two emission bands peaking at 500 and 380 nm were detected, the light output was about 80% of that for standard BGO scintillator, main decay constant was 10.4 +/- 0.1 ns. The obtained data allow us to consider the ZnO:Zn ceramics as a perspective scintillator. Finally, the investigation shows that other ZnO-based fast scintillators can be fabricated in the form of optical ceramics.

cond-mat.mtrl-sci↗

arXiv2010

Optical, luminescence, and scintillation properties of ZnO and ZnO:Ga ceramics

Uniaxial hot pressing has been used to obtain ceramics based on zinc oxide, and their optical, x-ray-structure, luminescence, and scintillation characteristics have been studied. It is shown that, by changing the concentration of the dopant (Ga) and the codopant (N), it is possible to change the intensities of the edge band (397.5 nm) and the intraband luminescence (510 nm) of the ZnO luminescence, as well as their ratio. Undoped ZnO ceramic has good transparency in the visible region and fairly high luminous yield: 9050 photons per MeV. Ceramic ZnO:Ga possesses intense edge luminescence with a falloff time of about 1 ns.

cond-mat.mtrl-sci↗

arXiv2010

Gamma Radiation Measurements and Dose Rates in Commonly Used Building Materials in Cyprus

A first comprehensive study is presented on radioactivity concentrations and dose rates in 87 commonly used materials, manufactured or imported in Cyprus, for building purposes. The natural radioactivity of K-40, Th-232, U-238 and Ra-226 is determined using high-resolution gamma ray spectroscopy. The respective dose rates and the associated radiological effect indices are also calculated. A comparison of the measured specific activity values with the corresponding world average values shows that most of them are below the world average activity values. The annual indoor effective dose rates received by an individual from three measured imported granites and four measured imported ceramics are found to be higher than the world upper limit value of 1 mSv y-1. Hence, these materials should have a restricted use according to their corresponding calculated activity concentration index values and the related EC 1999 guidelines.

physics.med-ph↗

arXiv2010

Mesonic Super Čerenkov-like effects in hadronic and nuclear media

Generalized mesonic Super-Čerenkov Radiations (SČR) are investigated. The energy behavior of the pionic refractive index in the low energy pionic SCR-sector is presented. We estimated that the true coherent SCR-pion emission is possible mainly in the SCRS-energy bands 190-315 MeV for all pions; 910-960 MeV only for positive pions, and 80-1000 GeV for all pions, in certain nuclear reactions. We predicted that SČR-pionic band will be enlarged for the pion energies higher than 80 GeV. The strong correlations between angle of SCR-pion emission and (meson and projectile)-energies are evidentiated. The spectral distributions of the SCR-pions are presented and the position of their maxima are estimated. The agreement with the available experimental data is discussed.

nucl-th↗

arXiv2010

Critical behavior of Binder ratios and ratios of higher order cumulants of conserved charges in QCD deconfinement phase transition

Binder liked ratios of baryon number are firstly suggested in relativistic heavy ion collisions. Using 3D-Ising model, the critical behavior of Binder ratios and ratios of high order cumulants of order parameter are fully presented. Binder ratio is shown to be a step function of temperature. The critical point is the intersection of the ratios of different system sizes between two platforms. From low to high temperature through the critical point, the ratios of third order cumulants change their values from negative to positive in a valley shape, and ratios of fourth order cumulants oscillate around zero. The normalized ratios, like the Skewness and Kurtosis, do not diverge with correlation length, in contrary with corresponding cumulants. Applications of these characters in search critical point in relativistic heavy ion collisions are discussed.

nucl-th↗

arXiv2010

Relativistic heavy-ion physics

The study of relativistic heavy-ion collisions is an important part of the LHC research programme at CERN. This emerging field of research focuses on the study of matter under extreme conditions of temperature, density, and pressure. Here we present an introduction to the general aspects of relativistic heavy-ion physics. Afterwards we give an overview of the accelerator facility at CERN and then a quick look at the ALICE project as a dedicated experiment for heavy-ion collisions.

nucl-th↗