Performance of the CMS Cathode Strip Chambers with Cosmic Rays

The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device in the CMS endcaps. Their performance has been evaluated using data taken during a cosmic ray run in fall 2008. Measured noise levels are low, with the number of noisy channels well below 1%. Coordinate resolution was measured for all types of chambers, and fall in the range 47 microns to 243 microns. The efficiencies for local charged track triggers, for hit and for segments reconstruction were measured, and are above 99%. The timing resolution per layer is approximately 5 ns

Aligning the CMS Muon Chambers with the Muon Alignment System during an Extended Cosmic Ray Run

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CMS physics technical design report : Addendum on high density QCD with heavy ions

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Unravelling the Ordered Phase of the Quintessential Hybrid Perovskite MAPbI3 – Thermophysics to the Rescue

Hybrid organic-inorganic perovskites continue to attract an enormous amount of attention, yet a robust microscopic picture of their different phases as well as the extent and nature of the disorder present remain elusive. Using specific-heat data along with high-resolution inelastic neutron scattering and ab initio modeling, we address this ongoing challenge for the case of the ordered phase of the quintessential hybrid perovskite MAPbI3. At low-temperatures, the specific heat of MAPbI3 reveals strong deviations from the Debye limit, a common feature of pure hybrid perovskites and their mixtures. We find that these deviations are exquisitely sensitive to the underlying low-energy phonon band structure, thus paving the way for a quantitative and robust assessment of available structural models beyond what has been possible to date. Our thermophysical analysis demonstrates that the (otherwise ordered) structure around the organic moiety is characterized by a substantial lowering of the local symmetry relative to what can be inferred from crystallographic studies. The ab initio phonon calculations also provide a means of exploring in detail the physical origin of the observed thermophysical anomalies, which can now be unequivocally associated with excitations of sub-Terahertz optical phonons responsible for translational and librational distortions of the octahedral units. To the best of our knowledge, this is the first time that such a model-selection protocol using thermophysical properties as key input has been deployed with success in the study of this important class of materials

Cation Dynamics as Structure Explorer in Hybrid Perovskites – the Case of MAPbI3

Hybrid organic-inorganic perovskites exhibit remarkable potential as cost-effective and high-efficiency materials for photovoltaic applications. Their exceptional chemical tunability opens further routes for optimizing their optical and electronic properties through structural engineering. Nevertheless, the extraordinary softness of the lattice, stemming from its interconnected organic-inorganic composition, unveils formidable challenges in their structural characterization. Here, by focusing on the quintessen tial methylammonium lead triiodide, MAPbI3, we combine first-principles modeling with high-resolution neutron scattering data to identify the key stationary points on its shallow potential energy landscape. This combined experimental and computa tional approach enables us to benchmark the performance of a collection of semi-local exchange-correlation functionals and to track the local distortions of the perovskite framework, hallmarked by the inelastic neutron scattering response of the organic cation. By conducting a thorough examination of structural distortions, we introduce the IKUR-PVP-1 structural dataset. This dataset contains nine mechanically stable structural models, each manifesting a distinct vibrational response. IKUR-PVP-1 con stitutes a valuable resource for assessing the thermal behavior in the low-temperature perovskite phase. In addition, it paves the way for the development of accurate force fields, enabling a comprehensive understanding of the interplay between structure and dynamics in MAPbI3 and related hybrid perovskites

Supplementary Information for Publication: Cation Dynamics as Structure Explorer in Hybrid Perovskites – the Case of MAPbI3

Collection of CASTEP *.phonon files according to IKUR-PVP-1 dataset, delivered as a part of the publication: Cation Dynamics as Structure Explorer in Hybrid Perovskites – the Case of MAPbI3 by Kacper Druzbicki, Pablo Gila-Herranz, Pelayo Marin-Villa, Mattia Gaboardi, Jeff Armstrong, and Felix Fernandez-Alonso

Cation dynamics as structure explorer in hybrid 0erovskites─The case of MAPbI3

Published as part of Crystal Growth & Design virtual special issue “Lattice Dynamics”.Hybrid organic–inorganic perovskites exhibit remarkable potential as cost-effective and high-efficiency materials for photovoltaic applications. Their exceptional chemical tunability opens further routes for optimizing their optical and electronic properties through structural engineering. Nevertheless, the extraordinary softness of the lattice, stemming from its interconnected organic–inorganic composition, unveils formidable challenges in structural characterization. Here, by focusing on the quintessential methylammonium lead triiodide, MAPbI3, we combine first-principles modeling with high-resolution neutron scattering data to identify the key stationary points on its shallow potential energy landscape. This combined experimental and computational approach enables us to benchmark the performance of a collection of semilocal exchange–correlation functionals and to track the local distortions of the perovskite framework, hallmarked by the inelastic neutron scattering response of the organic cation. By conducting a thorough examination of structural distortions, we introduce the IKUR-PVP-1 structural data set. This data set contains nine mechanically stable structural models, each manifesting a distinct vibrational response. IKUR-PVP-1 constitutes a valuable resource for assessing thermal behavior in the low-temperature perovskite phase. In addition, it paves the way for the development of accurate force fields, enabling a comprehensive understanding of the interplay between the structure and dynamics in MAPbI3 and related hybrid perovskites.Financial support from the Spanish Ministry of Science and Innovation (grant PID2020-114506GB-100 funded by MCIN/AEI/10.13039/501100011033) and the Basque government (grant PIBA-2021-0026) is gratefully acknowledged. Grant PRE2021-097712 to support P.M.V. has been funded by MCIN/AEI/10.13039/501100011033 and the European Social Fund Programme “Investing in Your Future”. We acknowledge generous HPC resources from PL-Grid Infrastructure (grant IDs: plghybrids; plghybrids2022; and plghybrids2023). We further acknowledge the Spanish Supercomputing Network (RES Activity: QHS-2023-1-0027) and the computational resources from the Donostia International Physics Center (DIPC; Atlas Facility). M.G. wishes to thank Chiara Milanese (University of Pavia) for the support. We gratefully acknowledge the financial support received from the IKUR Strategy under the collaboration agreement between the Ikerbasque Foundation and the Materials Physics Center, on behalf of the Department of Education of the Basque government.Peer reviewe

CMS physics technical design report: Addendum on high density QCD with heavy ions

This report presents the capabilities of the CMS experiment to explore the rich heavy-ion physics programme offered by the CERN Large Hadron Collider (LHC). The collisions of lead nuclei at energies ,will probe quark and gluon matter at unprecedented values of energy density. The prime goal of this research is to study the fundamental theory of the strong interaction - Quantum Chromodynamics (QCD) - in extreme conditions of temperature, density and parton momentum fraction (low-x). This report covers in detail the potential of CMS to carry out a series of representative Pb-Pb measurements. These include "bulk" observables, (charged hadron multiplicity, low pT inclusive hadron identified spectra and elliptic flow) which provide information on the collective properties of the system, as well as perturbative probes such as quarkonia, heavy-quarks, jets and high pT hadrons which yield "tomographic" information of the hottest and densest phases of the reaction.0info:eu-repo/semantics/publishe

The CMS experiment at the CERN LHC

The Compact Muon Solenoid (CMS) detector is described. The detector operates at the Large Hadron Collider (LHC) at CERN. It was conceived to study proton-proton (and lead-lead) collisions at a centre-of-mass energy of 14 TeV (5.5 TeV nucleon-nucleon) and at luminosities up to 10(34)cm(-2)s(-1) (10(27)cm(-2)s(-1)). At the core of the CMS detector sits a high-magnetic-field and large-bore superconducting solenoid surrounding an all-silicon pixel and strip tracker, a lead-tungstate scintillating-crystals electromagnetic calorimeter, and a brass-scintillator sampling hadron calorimeter. The iron yoke of the flux-return is instrumented with four stations of muon detectors covering most of the 4 pi solid angle. Forward sampling calorimeters extend the pseudo-rapidity coverage to high values (vertical bar eta vertical bar <= 5) assuring very good hermeticity. The overall dimensions of the CMS detector are a length of 21.6 m, a diameter of 14.6 m and a total weight of 12500 t