Reduction of light output of plastic scintillator tiles during irradiation at cold temperatures and in low-oxygen environments

The advent of the silicon photomultiplier has allowed the development of highly segmented calorimeters using plastic scintillator as the active media, with photodetectors embedded in the calorimeter, in dimples in the plastic. To reduce the photodetector's dark current and radiation damage, the high granularity calorimeter designed for the high luminosity upgrade of the CMS detector at CERN's Large Hadron Collider will be operated at a temperature of about -30$^\circ$C. Due to flammability considerations, a low oxygen environment is being considered. However, the radiation damage to the plastic scintillator during irradiation in this operating environment needs to be considered. In this paper, we present measurements of the relative decrease of light output during irradiation of small plastic scintillator tiles read out by silicon photomultipliers. The irradiations were performed using a $^{60}\mathrm{Co}$ source both to produce the tiles' light and as a source of ionizing irradiation at dose rates of 0.3, 1.3, and $1.6\,$Gy/hr, temperatures of -30, -15, -5, and 0$^\circ$C, and with several different oxygen concentrations in the surrounding atmosphere. The effect of the material used to wrap the tile was also studied. Substantial temporary damage, which annealed when the sample was warmed, was seen during the low-temperature irradiations, regardless of the oxygen concentration and wrapping material. The relative light loss was largest with 3M$^{\tiny \textrm{TM}}$ Enhanced Specular Reflector Film wrapping and smallest with no wrapping, although due to the substantially higher light yield with wrapping, the final light output is largest with wrapping. The light loss was less at warmer temperatures. Damage with $3\%$ oxygen was similar to that in standard atmosphere. Evidence of a plateau in the radical density was seen for the 0$^\circ$C data

Effects of oxygen on the optical properties of phenyl-based scintillators during irradiation and recovery

Plastic scintillators are a versatile and inexpensive option for particle detection, which is why the largest particle physics experiments, CMS and ATLAS, use them extensively in their calorimeters. One of their challenging aspects, however, is their relatively low radiation hardness, which might be inadequate for very high luminosity future projects like the FCC-hh. In this study, results on the effects of ionizing radiation on the optical properties of plastic scintillator samples are presented. The samples are made from two different matrix materials, polystyrene and polyvinyltoluene, and have been irradiated at dose rates ranging from $2.2\,$Gy/h up to $3.4\,$kGy/h at room temperature. An internal boundary that separates two regions of different indices of refraction is visible in the samples depending on the dose rate, and it is compatible with the expected oxygen penetration depth during irradiation. The dose rate dependence of the oxygen penetration depth for the two matrix materials suggests that the oxygen penetration coefficient differs for PS and PVT. The values of the refractive index for the internal regions are elevated compared to those of the outer regions, which are compatible with the indices of unirradiated samples.Comment: Replaced with published version. Added journal DOI. 30 pages, 15 figures. Published in Nuclear Instruments and Methods in Physics Research Section

Summary of the Very Large Hadron Collider Physics and Detector Workshop

One of the options for an accelerator beyond the LHC is a hadron collider with higher energy. Work is going on to explore accelerator technologies that would make such a machine feasible. This workshop concentrated on the physics and detector issues associated with a hadron collider with an energy in the center of mass of the order of 100 to 200 TeV

Using decoction of some vitamin C enriched plants for the management of COVID-19 in Jos, Nigeria: A case report

The worldwide influence of coronavirus disease 2019 (COVID-19) pandemic compelled the global health organizations to prioritize the situation over all other related community health issues. The lack of specific treatment modalities against COVID-19 is a major concern nowadays. Here is a case of a 44-year-old man of 176 cm height and 87 kg body weight, who took some powdered mixture equally composed of bitter kola, cinnamon, garlic, ginger, and turmeric sweetened with three teaspoons full of honey. All ingredients were dissolved in 100 ml hot water and taken three times a day during isolation as a positive COVID-19 patient and reversed all associated signs and symptoms after 7 days as confirmed with rapid diagnostic techniques (RDTs). This case revealed that homogenized herbal tea in Jos Nigeria possesses a potential therapeutic that could be a treatment protocol against COVID-19

Limits on WWgamma and WWZ Couplings from W Boson Pair Production

The results of a search for W boson pair production in pbar-p collisions at sqrt{s}=1.8 TeV with subsequent decay to emu, ee, and mumu channels are presented. Five candidate events are observed with an expected background of 3.1+-0.4 events for an integrated luminosity of approximately 97 pb^{-1}. Limits on the anomalous couplings are obtained from a maximum likelihood fit of the E_T spectra of the leptons in the candidate events. Assuming identical WWgamma and WWZ couplings, the 95 % C.L. limits are -0.62<Delta_kappa<0.77 (lambda = 0) and -0.53<lambda<0.56 (Delta_kappa = 0) for a form factor scale Lambda = 1.5 TeV.Comment: 10 pages, 1 figure, submitted to Physical Review

Search for a Fourth Generation Charge -1/3 Quark via Flavor Changing Neutral Current Decay

We report on a search for pair production of a fourth generation charge -1/3 quark (b') in pbar p collisions at sqrt(s) = 1.8 TeV at the Fermilab Tevatron using an integrated luminosity of 93 pb^-1. Both quarks are assumed to decay via flavor changing neutral currents (FCNC). The search uses the signatures gamma + 3 jets + mu-tag and 2 gamma + 2 jets. We see no significant excess of events over the expected background. We place an upper limit on the production cross section times branching fraction that is well below theoretical expectations for a b' quark decaying exclusively via FCNC for b' quark masses up to m(Z) + m(b).Comment: Eleven pages, two postscript figures, submitted to Physical Review Letter

Direct Measurement of the Top Quark Mass at D0

We determine the top quark mass m_t using t-tbar pairs produced in the D0 detector by \sqrt{s} = 1.8 TeV p-pbar collisions in a 125 pb^-1 exposure at the Fermilab Tevatron. We make a two constraint fit to m_t in t-tbar -> b W^+bbar W^- final states with one W boson decaying to q-qbar and the other to e-nu or mu-nu. Likelihood fits to the data yield m_t(l+jets) = 173.3 +- 5.6 (stat) +- 5.5 (syst) GeV/c^2. When this result is combined with an analysis of events in which both W bosons decay into leptons, we obtain m_t = 172.1 +- 5.2 (stat) +- 4.9 (syst) GeV/c^2. An alternate analysis, using three constraint fits to fixed top quark masses, gives m_t(l+jets) = 176.0 +- 7.9 (stat) +- 4.8 (syst) GeV/C^2, consistent with the above result. Studies of kinematic distributions of the top quark candidates are also presented.Comment: 43 pages, 53 figures, 33 tables. RevTeX. Submitted to Phys. Rev.

Search for First Generation Scalar Leptoquark Pairs in ppbar Collisions at sqrt(s)=1.8 TeV

We have searched for first generation scalar leptoquark (LQ) pairs in the enu+jets channel using ppbar collider data (integrated luminosity= 115 pb^-1) collected by the DZero experiment at the Fermilab Tevatron during 1992-96. The analysis yields no candidate events. We combine the results with those from the ee+jets and nunu+jets channels to obtain 95% confidence level (CL) upper limits on the LQ pair production cross section as a function of mass and of beta, the branching fraction to a charged lepton. Comparing with the next-to-leading order theory, we set 95% CL lower limits on the LQ mass of 225, 204, and 79 GeV/c^2 for beta=1, 1/2, and 0, respectively.Comment: 14 pages, 4 figures, submitted to Physical Review Letters Replaced to correct visitor addresse

The Search for Supersymmetry at the Tevatron Collider

We review the status of searches for Supersymmetry at the Tevatron Collider. After discussing the theoretical aspects relevant to the production and decay of supersymmetric particles at the Tevatron, we present the current results for Runs Ia and Ib as of the summer of 1997. To appear in the book "Perspectives in Supersymmetry", edited by G.L. Kane, World Scientific.Comment: 84 pages with 31 figures imbedded using psfig.tex. Uses sprocl.st

Measurement of the WW Boson Mass

A measurement of the mass of the $W$ boson is presented based on a sample of 5982 $W \rightarrow e \nu$ decays observed in $p\overline{p}$ collisions at $\sqrt{s}$ = 1.8~TeV with the D\O\ detector during the 1992--1993 run. From a fit to the transverse mass spectrum, combined with measurements of the $Z$ boson mass, the $W$ boson mass is measured to be $M_W = 80.350 \pm 0.140 (stat.) \pm 0.165 (syst.) \pm 0.160 (scale) GeV/c^2$.Comment: 12 pages, LaTex, style Revtex, including 3 postscript figures (submitted to PRL