We review the main results obtained by the BRAHMS Collaboration on the properties of hot and dense hadronic and partonic matter produced in ultrarelativistic heavy ion collisions at RHIC. A ...particular focus of this paper is to discuss to what extent the results collected so far by BRAHMS, and by the other three experiments at RHIC, can be taken as evidence for the formation of a state of deconfined partonic matter, the so-called quark–gluon plasma (QGP). We also discuss evidence for a possible precursor state to the QGP, i.e., the proposed color glass condensate.
Abstract
A systematic investigation of Planacon MCP-PMTs was performed using 64 XP85002/ FIT-Q photosensors. These devices are equipped with microchannel plates of reduced resistance. Results of a ...study of their gain stability over time and saturation level in terms of the average anode current are presented. This information allows one to determine the lower limit of the MCP resistance for stable Planacon operation. The spread of the electron multiplication characteristics for the entire production batch is also presented, indicating the remarkably low voltage requirements of these MCP-PMTs. Detection efficiency and noise characteristics, such as dark count rate and afterpulsing level, are also reviewed.
We have measured and compared the characteristics of ALD-coated Planacon® MCP-PMTs (XP85112/A1-Q-L) with their non-ALD counterparts (XP85012/A1-Q). While the latter show excellent performance, the ...ALD-coated sensors have surprisingly low current saturation levels (∼ two orders of magnitude lower than expected) and extremely high gain recovery time (more than 7 orders of magnitude higher than expected). We suspect that these problems might be caused by the unexpected side-effects of the ALD process. To make a definite conclusion, more samples need to be tested, preferably from different production runs. If our observation were confirmed, it would mean a serious technological setback for ALD-coated MCP-PMTs.
Recent highlights from BRAHMS Bearden, I G
Journal of physics. G, Nuclear and particle physics,
08/2007, Letnik:
34, Številka:
8
Journal Article, Conference Proceeding
We present the behavior of the cost-effective Planacon MCP-PMTs with 25μm pore diameter in the presence of axial magnetic fields up to 0.5 T. Having a batch of 62 devices of the same type, two ...MCP-PMTs were selected and their gain variation measured in different magnetic fields. These two otherwise identical devices satisfied the selection criteria by requiring the lowest (1.15 kV) and one of the highest (1.4 kV) bias voltage values to achieve a given gain. Both MCP-PMTs have a nearly identical tolerance of the strong magnetic field despite the significant difference in the bias voltage. This clarifies the mechanism of the B-field influence on the MCP-PMT gain, emphasizing the importance of the intrinsic parameters of the MCP emissive coating rather than external parameters, such as the total bias voltage. By evaluating the dependence of both gain and timing parameters on the magnetic field strength, we confirm the operability of such MCP-PMTs in strong magnetic fields in spite of the relatively large pore diameter and low bias voltage required for a given gain.
A multiyear study in the C-111 canal system and associated sites in Florida Bay was undertaken to determine the potential pesticide risk that exists in South Florida. After the examination of ...extensive pesticide concentration data in surface water, tissues, and semipermeable membrane devices (SPMDs), canal contamination seems to be derived from the extensive agricultural production that drains into the C-111 canal. The results of this study indicate that runoff from agricultural processes led to quantifiable pesticide residues in both canal and bay surface water, which occasionally exceeded current water quality criteria. The major pesticide of concern was endosulfan, which was detected at 100% of the sites sampled. Endosulfan exposure did not cause any acute effects in fish and crustaceans deployed in field bioassays. Chronic effects were observed in copepods, clams, and oysters but could not be attributed to endosulfan exposure. The decision to alter the C-111 canal flow and allow increased freshwater flow into the adjacent Everglades National Park may result in discharges of pesticides into the Everglades. Continued monitoring in this area is needed during this change in flow regime. Keywords: Endosulfan; Florida Bay; South Florida; semipermeable membrane devices; oysters; copepods; clams
From measured rapidity distributions
d
N
/
d
y
of
p,
p
¯
in central Au+Au collisions at
s
N
N
=
200
GeV
, we find an average rapidity loss per participant nucleon is
2.0
±
0.2
units of rapidity. We ...have also measured high transverse momentum particles. For central
A
u
+
A
u
collisions, we observe a suppression at both
η
=
0
,
2.2
, while for peripheral collisions there is no evidence of this suppression. In
d
+
A
u
, there is an enhancement at midrapidity, while at forward rapidities the spectra become suppressed.
We present a measurement of π−/π+, K−/K+ and p¯/p from p+p collisions at s=200 GeV over the rapidity range 0<y<3.4. For pT<2.0 GeV/c we see no significant transverse momentum dependence of the ...ratios. All three ratios are independent of rapidity for y≲1.5 and then steadily decline from y∼1.5 to y∼3. The π−/π+ ratio is below unity for y>2.0. The p¯/p ratio is very similar for p+p and 20% central Au+Au collisions at all rapidities. In the fragmentation region the three ratios seem to be independent of beam energy when viewed from the rest frame of one of the protons. Theoretical models based on quark–diquark breaking mechanisms overestimate the p¯/p ratio up to y≲3. Including additional mechanisms for baryon number transport such as baryon junctions leads to a better description of the data.
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