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 the LHC energies. Our hypothesis ...was based on experimental data, which raised the idea of a finite formation time for the produced medium. At the RHIC energy and in low-density corona region, this time reaches about 2 fm/
c
. Following this hypothesis, the nuclear modification factor
R
AA
at high
p
t
should be independent on particle momentum, and the azimuthal anisotropy of high
p
t
particles,
v
2
, should be finite. A separate prediction held that, at the LHC energy, the formation time in the corona region should be about 1 fm/
c
. New LHC data 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 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 the RHIC energy. We also show that the observed at the LHC dependence of
v
2
at high
p
t
and our previous predictions agree.
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 Fe
55
and Am
241
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.
We present 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 300–750 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. We present the upper limits at a 95% confidence level on electron neutrino–heavy neutrino mixing element,
, in the mass matrix. New upper limits are in the range of (2–4) × 10
–4
which are at least one order of magnitude lower than the existing data in 300–800 keV mass range.
We present a brief review of experimental status in searching for hypothetical sterile neutrino in nuclear decay in laboratory testing. The main idea is based on search for an additional small ...component in the β-spectrum or a shift in the internal electron conversion energy. For example, in a three-body β-decay it looks like a kink in the continuous spectrum shifted by the value of sterile neutrino mass from the spectrum endpoint. After a short general motivation for such a search we discuss the way how to find sterile neutrino in the nuclear β-decay and present the current status of upper limits on sterile neutrino mixing with electron antineutrino. The advantages and problems arising in the precise measurements of β-spectrum are demonstrated on the basis of the “Troitsk nu-mass” experiment by presenting the all measurement and analysis procedures in details. At the end we discuss the nearest future of such experiments.
A Hadron Blind Detector (HBD) has been developed, constructed and successfully operated within the PHENIX detector at RHIC. The HBD is a Cherenkov detector operated with pure
CF
4
. It has a 50
cm ...long radiator directly coupled in a windowless configuration to a readout element consisting of a triple GEM stack, with a CsI photocathode evaporated on the top surface of the top GEM and pad readout at the bottom of the stack. This paper gives a comprehensive account of the construction, operation and in-beam performance of the detector.
Sterile neutrinos are a minimal extension of the standard model of particle physics. A promising model-independent way to search for sterile neutrinos is via high-precision β-spectroscopy. The ...Karlsruhe tritium neutrino (KATRIN) experiment, equipped with a novel multi-pixel silicon drift detector focal plane array and read-out system, named the TRISTAN detector, has the potential to supersede the sensitivity of previous laboratory-based searches. In this work we present the characterization of the first silicon drift detector prototypes with electrons and we investigate the impact of uncertainties of the detector's response to electrons on the final sterile neutrino sensitivity.
The possible existence of a finite formation time of strongly interacting plasma in nuclear collisions at RHIC is demonstrated from recent experimental data. To show this, we use a simple model based ...on Monte Carlo simulation of nucleus-nucleus collisions with realistic nuclear density distribution. The most striking feature of the experimental data—an absence of absorption of high transverse momentum pions in the reaction plane direction for mid-peripheral collisions—points to the presence of a surface zone with no absorption and strong suppression in the inner core. A natural interpretation of such a zone could be the plasma formation time T ~ 2–3 fm/c. The existence of a formation time could dramatically change our understanding of many experimentally observed features. With this assumption, we describe the angular anisotropy of high transverse momentum pions with respect to the reaction plane and the centrality dependence of the nuclear modification factor in Au + Au and Cu + Cu collisions.
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