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During the upcoming High Luminosity phase of the Large Hadron Collider (HL-LHC), the integrated luminosity of the accelerator will increase to 3000 fb$^{-1}$. The expected experimental conditions in that period in terms of background rates, event pileup, and the probable aging of the current detectors present a challenge for all the existing experiments at the LHC, including the Compact Muon Solenoid (CMS) experiment. To ensure a highly performing muon system for this period, several upgrades of the Resistive Plate Chamber (RPC) system of the CMS are currently being implemented. These include the replacement of the readout system for the present system, and the installation of two new RPC stations with improved chamber and front-end electronics designs. The current overall status of this CMS RPC upgrade project is presented.

A quantum Langevin model, similar to models used recently for optomechanics, was used to predict intermodulation phonon sidebands (IPS). Ab initio calculations of anharmonic phonons in rocksalt NaBr showed these spectral features as "many-body effects". Modern inelastic neutron scattering measurements on a crystal of NaBr at 300K revealed diffuse intensity at high phonon energy from a predicted upper IPS. The transverse optical (TO) part of the new features originates from phonon intermodulation between the transverse acoustic (TA) and TO phonons. The longitudinal optical (LO) spectral features originate from three-phonon coupling between the TA modes and the TO lattice modes. The partner lower IPS proves to be an "intrinsic localized mode". Interactions with the thermal bath broaden and redistribute the spectral weight of the IPS pair. These sidebands are a probe of anharmonicity and quantum noise, which originate from interactions between the phonons in NaBr.

The expected radiation background in the CMS RPC system has been studied using the MC prediction with the CMS FLUKA simulation of the detector and the cavern. The MC geometry used in the analysis describes very accurately the present RPC system but still does not include the complete description of the RPC upgrade region with pseudorapidity $1.9 < \lvert \eta \rvert < 2.4$. Present results will be updated with the final geometry description, once it is available. The radiation background has been studied in terms of expected particle rates, absorbed dose and fluence. Two High Luminosity LHC (HL-LHC) scenarios have been investigated - after collecting $3000$ and $4000$ fb$^{-1}$. Estimations with safety factor of 3 have been considered, as well., Comment: 6 pages, Conference proceeding for the 2020 Resistive Plate Chambers and Related Detectors. Minor revision of the report, the results remain unchanged. Three new plots are added and some details were explained better

All phonons in a single crystal of NaBr were measured by inelastic neutron scattering at temperatures of 10, 300 and 700 K. Even at 300 K the phonons, especially the longitudinal-optical (LO) phonons, showed large shifts in frequencies, and showed large broadenings in energy owing to anharmonicity. Ab initio computations were first performed with the quasiharmonic approximation (QHA), in which the phonon frequencies depend only on $V$, and on $T$ only insofar as it alters $V$ by thermal expansion. This QHA was an unqualified failure for predicting the temperature dependence of phonon frequencies, even 300 K, and the thermal expansion was in error by a factor of four. Ab initio computations that included both anharmonicity and quasiharmonicity successfully predicted both the temperature dependence of phonons and the large thermal expansion of NaBr. The frequencies of LO phonon modes decrease significantly with temperature owing to the real part of the phonon self-energy from explicit anhamonicity, originating from the cubic anharmonicity of nearest-neighbor Na-Br bonds. Anharmonicity is not a correction to the QHA predictions of thermal expansion and thermal phonon shifts, but dominates the behavior., Comment: 3 figures, 1 table, and the Supplementary Material appended

Recent X-ray observations in the central compact remnant of Puppis A and other young pulsars have provided convincing evidence about the anti-magnetar nature of the so-called central compact objects (CCOs). The measured period derivative, corrected by the proper movement, provides exceptionally low superficial magnetic fields for such sources. Using the dipole radiation canonical model, the superficial magnetic field of the CCO (RX J0822-4300) in Puppis A was estimated to be $B\simeq 2.9 \times 10^{10}$ G. In this paper, we present a numerical model to interpret the unusual magnetic-field behavior in RX J0822-4300. Using the magnetohydrodynamic simulations during the hypercritical accretion phase, we propose that a variety of MeV neutrinos is created given evidence about the submergence of the magnetic field in the pulsar. We investigate the production, propagation, oscillations, and detection of MeV neutrinos from this source. The detection of neutrino events with their flavor ratios would be a compelling signature of the decreasing evolution of the magnetic field not only in RX J0822-4300 but also in CCO candidates., Comment: 16 pages, 9 figures. Accepted for publication in PASP

The measurement of the period and period derivative, and the canonical model of dipole radiation have provided a method to estimate the low superficial magnetic fields in the so-called Central Compact Objects (CCOs). In the present work, a scenario is introduced in order to explain the magnetic behavior of such CCOs. Based on magnetohydrodynamic simulations of the post core-collapse supernova phase during the hypercritical accretion episode, we argue that the magnetic field of a newborn neutron star could have been early buried. During this phase, thermal neutrinos are created mainly by the pair annihilation, plasmon decay, photo-neutrino emission and other processes. We study the dynamics of these neutrinos in this environment and also estimate the number expected of the neutrino events with their flavor ratios on Earth. The neutrino burst is the only viable observable that could provide compelling evidence of the hypercritical phase and therefore, the hidden magnetic field mechanism as the most favorable scenario to explain the anomalous low magnetic fields estimated for CCOs., Comment: 18 pages, 7 figures and 4 tables. Accepted for publication in PRD. New reference was added

Cassiopeia A the youngest supernova remnant known in the Milky Way is one of the brightest radio sources in the sky and a unique laboratory for supernova physics. Although its compact remnant was discovered in 1999 by the Chandra X-Ray Observatory, nowadays it is widely accepted that a neutron star lies in the center of this supernova remnant. In addition, new observations suggest that such neutron star with a low magnetic field and evidence of a carbon atmosphere could have suffered a hypercritical accretion phase seconds after the explosion. Considering this hypercritical accretion episode, we compute the neutrino cooling effect, the number of events and neutrino flavor ratios expected on Hyper-Kamiokande Experiment. The neutrino cooling effect (the emissivity and luminosity of neutrinos) is obtained through numerical simulations performed in a customized version of the FLASH code. Based on these simulations, we forecast that the number of events expected on the Hyper-Kamiokande Experiment is around 3195. Similarly, we estimate the neutrino flavor ratios to be detected considering the neutrino effective potential due to the thermal and magnetized plasma and thanks to the envelope of the star. It is worth noting that our estimates correspond to the only trustworthy method for verifying the hypercritical phase and although this episode took place 330 years ago, at present supernova remnants with these similarities might occur thus confirming our predictions for this phase., Comment: Accepted for publication in MNRAS (14 pages, 6 figures)

Using axisymmetrical numerical simulations, we revisit the gravitational drag felt by a gravitational Plummer sphere with mass M and core radius Rs, moving at constant velocity V0 through a background homogeneous medium of adiabatic gas. Since the potential is non-diverging, there is no gas removal due to accretion. When Rs is larger than the Bondi radius RB, the perturbation is linear at every point and the drag force is well fitted by the time-dependent Ostriker's formula with r_{min}= 2.25Rs, where r_{min} is the minimum impact parameter in the Coulomb logarithm. In the deep nonlinear supersonic regime (Rs<< RB), the minimum radius is no longer related with Rs but with RB. We find r_min=3.3mach^{-2.5}RB, for Mach numbers of the perturber between $1.5$ and $4$, although r_{min} = 2\mach^{-2}RB=2GM/V0^{2} also provides a good fit at mach>2. As a consequence, the drag force does not depend sensitively on the nonlinearity parameter RB/Rs, for RB/Rs-values larger than a certain critical value. We show that our generalized Ostriker's formula for the drag force is more accurate than the formula suggested by Kim & Kim (2009)., Comment: 8 pages, 9 figures, accepted for publication in ApJ