Following our earlier finding based on RHIC data on the dominant jet production from nucleus corona region, we reconsider this effect in nucleus-nucleus collisions at LHC energy. Our hypothesis was ...based on experimental data, which raised the idea of a finite formation time for the produced medium. At RHIC energy and in low density corona region this time reaches about 2 fm/c. All observed high p_t particles are produced in the corona region and have a chance to escape during this 2 fm/c. After that, the formed high density matter absorbs all jets. Following this hypothesis, the nuclear modification factor R_{AA} should be independent on particle momentum and be flat versus p_t. At the same time, we describe the finite azimuthal anisotropy of high p_t particles, v_2. A separate prediction held that, at LHC energy, the formation time in the corona region should be two times smaller, about 1 fm/c. New data at LHC show that R_{AA} is not flat and is rising with p_t. We add to our original hypothesis an assumption that a fast parton traversing the produced medium loses the fixed portion of its energy. A shift of about 7 GeV (I would call it as a parton binding energy) from the original power law p^{-6} production cross section in pp explains well all the observed R_{AA} dependencies. The shift of about 7 GeV is also valid at RHIC energy, where the cross section follows a power law with about p^{-8} and this shift explains a very slow rise of R_{AA} seen for neutral pions with p_t above 15 GeV/c. We also show that the observed at LHC dependence of v_2 at high p_t and our previous predictions agree.
We present a reanalysis of the experimental data of electron capture in \(^7\)Be embedded in Ta which have been published by other authors. Our goal is to set upper limits on a mixture of electron ...neutrino with a possible right-handed heavy neutrino in the 150--800 keV mass range. In the published experiment a \(^7\)Li recoil energy spectrum in the 20--200 eV range was measured. In case of electron capture with emission of a heavy neutrino, the recoil spectrum should be shifted to the lower energies. We search for an additional Gauss-shaped structure with the same energy width as the main K-shell transition peak. For this we digitize the published spectrum curve, find the energy resolution, calculate the moving sum of the events along the spectrum in the energy interval of about 3 sigma of energy resolution. Then we use the statistical error of this sum to exclude at some level the appearance of an additional peak. Finally, we present the upper limits at a 95\% confidence level on electron neutrino -- heavy neutrino mixing element, \(U^2\), in the mass matrix. New upper limits are at least one order of magnitude lower than the existing data in 300--800 keV mass range.
This paper describes the methods and presents the results of the "Troitsk Nu-mass" experiment spectrometer cleanup after the in\ner volume (40 m
3
) and surfaces (160 m
2
) were contaminated by ...5.2 GBq of tritium. The Troitsk Nu-mass experiment of the Institute for Nuclear Research of the Russian Academy of Sciences (Moscow) is designed to measure the spectrum of electrons from tritium decays in order to search for hypothetical particles-sterile neutrinos. Due to some equipment failures, the spectrometer internal volume was contaminated with tritium. The contamination made measurements impossible, and the research program stopped. Different methods were used for cleanup: vacuum extraction, hydrogen soaks, and water vapor soaks. As a result of detritiation, the background level of the main detector of the Troitsk Nu-mass spectrometer was reduced approximately by more than ten times, which made it possible to resume work. The results are consistent with the literature data obtained earlier for normal conditions in the air and can be used for detritiation of similar installations.
We present a measurement of the transverse single-spin asymmetry for π0 and η mesons in p↑+ p collisions in the pseudorapidity range |η| < 0.35 and at a center-of-mass energy of 200 GeV with the ...PHENIX detector at the Relativistic Heavy Ion Collider. In comparison with previous measurements in this kinematic region, these results have factor-of-3-smaller uncertainties. As hadrons, π0 and η mesons are sensitive to both initial- and final-state nonperturbative effects for a mix of parton flavors. Comparisons of the differences in their transverse single-spin asymmetries have the potential to disentangle the possible effects of strangeness, isospin, or mass. These results can constrain the twist-3 trigluon collinear correlation function as well as the gluon Sivers function.
The PHENIX experiment has studied nuclear effects in p+Al and p+Au collisions at sNN=200GeV on charged hadron production at forward rapidity (1.4<η<2.4, p-going direction) and backward rapidity ...(-2.2<η<-1.2, A-going direction). Such effects are quantified by measuring nuclear modification factors as a function of transverse momentum and pseudorapidity in various collision multiplicity selections. In central p+Al and p+Au collisions, a suppression (enhancement) is observed at forward (backward) rapidity compared to the binary scaled yields in p+p collisions. The magnitude of enhancement at backward rapidity is larger in p+Au collisions than in p+Al collisions, which have a smaller number of participating nucleons. However, the results at forward rapidity show a similar suppression within uncertainties. The results in the integrated centrality are compared with calculations using nuclear parton distribution functions, which show a reasonable agreement at the forward rapidity but fail to describe the backward rapidity enhancement.
We report the transverse single-spin asymmetries of J/ψ production at forward and backward rapidity, 1.2<|y|<2.2, as a function of J/ψ transverse momentum (pT) and Feynman-x (xF). The data analyzed ...were recorded by the PHENIX experiment at the Relativistic Heavy Ion Collider in 2015 from p+p, p+Al, and p+Au collisions with transversely polarized proton beams at sNN=200 GeV. At this collision energy, single-spin asymmetries for heavy-flavor particle production of p+p collisions provide access to the spin-dependent gluon distribution and higher-twist correlation functions inside the nucleon, such as the gluon Qiu-Sterman and trigluon correlation functions. Proton+nucleus collisions offer an excellent opportunity to study nuclear effects on the correlation functions. The data indicate a positive asymmetry at the two-standard-deviation level in the p+p data for 2 GeV/c<pT<10 GeV/c at backward rapidity and negative asymmetries at the two-standard-deviation level in the p+Au data for pT<2 GeV/c at both forward and backward rapidity, while in p+Al collisions the asymmetries are consistent with zero within the range of experimental uncertainties.
Presented are the first measurements of the transverse single-spin asymmetries (AN) for neutral pions and eta mesons in p+Au and p+Al collisions at sNN=200 GeV in the pseudorapidity range |η|
We present the results of tuning and calibration of the detector electronics in the signal digitization mode. The goal of the experiment is to search for a possible sterile neutrino signature in ...tritium beta-decay. The read-out electronics work in direct oscilloscope mode, which requires to optimize time frame the with the goal to minimize noise and energy resolution. We use a 7-pixel silicon drift detector (SDD) and a CMOS charge sensitive preamplifier with very low integration capacitor. Amplifier forms a slowly rising output shape and operates in pulse-reset mode. The 125 MHz ADC digitizes the signals. Using calibration data from Fe55 and Am241 gamma sources we check triangular and trapezoid digital filters to obtain the best noise and energy resolution performance. We are also examining the option to differentiate the output signal.
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