Search results for "CMS"
showing 10 items of 104 documents
Observation of light-by-light scattering in ultraperipheral Pb+Pb collisions with the ATLAS detector
2019
This Letter describes the observation of the light-by-light scattering process, γγ→γγ, in Pb+Pb collisions at √sNN=5.02 TeV. The analysis is conducted using a data sample corresponding to an integrated luminosity of 1.73 nb−1, collected in November 2018 by the ATLAS experiment at the LHC. Light-by-light scattering candidates are selected in events with two photons produced exclusively, each with transverse energy EγT>3 GeV and pseudorapidity |ηγ|<2.4, diphoton invariant mass above 6 GeV, and small diphoton transverse momentum and acoplanarity. After applying all selection criteria, 59 candidate events are observed for a background expectation of 12±3 events. The observed excess of events…
Phthalate esters in products and materials which come into contact with humans. GC-MS analysis
2013
Study of ordered hadron chains with the ATLAS detector
2017
The analysis of the momentum difference between charged hadrons in high-energy proton-proton collisions is performed in order to study coherent particle production. The observed correlation pattern agrees with a model of a helical QCD string fragmenting into a chain of ground-state hadrons. A threshold momentum difference in the production of adjacent pairs of charged hadrons is observed, in agreement with model predictions. The presence of low-mass hadron chains also explains the emergence of charge-combination-dependent two-particle correlations commonly attributed to Bose-Einstein interference. The data sample consists of 190 μb-1 of minimum-bias events collected with proton-proton colli…
Charm-quark fragmentation fractions and production cross section at midrapidity in pp collisions at the LHC
2022
Physical review / D 105(1), L011103 (2022). doi:10.1103/PhysRevD.105.L011103
Measurement of matter-antimatter differences in beauty baryon decays
2017
Differences in the behaviour of matter and antimatter have been observed in $K$ and $B$ meson decays, but not yet in any baryon decay. Such differences are associated with the non-invariance of fundamental interactions under the combined charge-conjugation and parity transformations, known as $C\!P$ violation. Using data from the LHCb experiment at the Large Hadron Collider, a search is made for $C\!P$-violating asymmetries in the decay angle distributions of $\Lambda^0_b$ baryons decaying to $p\pi^-\pi^+\pi^-$ and $p\pi^-K^+K^-$ final states. These four-body hadronic decays are a promising place to search for sources of $C\!P$ violation both within and beyond the Standard Model of particle…
Long-lived particles at the energy frontier: the MATHUSLA physics case
2019
We examine the theoretical motivations for long-lived particle (LLP) signals at the LHC in a comprehensive survey of Standard Model (SM) extensions. LLPs are a common prediction of a wide range of theories that address unsolved fundamental mysteries such as naturalness, dark matter, baryogenesis and neutrino masses, and represent a natural and generic possibility for physics beyond the SM (BSM). In most cases the LLP lifetime can be treated as a free parameter from the $\mu$m scale up to the Big Bang Nucleosynthesis limit of $\sim 10^7$m. Neutral LLPs with lifetimes above $\sim$ 100m are particularly difficult to probe, as the sensitivity of the LHC main detectors is limited by challenging …
Polycyclic aromatic hydrocarbons (PAHs) in indoor dust matter of Palermo (Italy) area: Extraction, GC–MS analysis,distribution and sources
2008
Abstract Studies on indoor pollution are important since people spend more than 80% of their time indoor environments. In this work the method for PAHs analysis in indoor dust (used as passive sampler) and the results relative to samples collected in the area of Palermo are reported. Dust samples for analysis were collected from 45 indoor environments. Total PAHs concentrations in indoor dusts ranged from 36 to 34 453 μg kg −1 d.w. To correlate indoor and outdoor pollution we analyze, also, the particulate matter and PAHs levels samples collected in four stations. The percentage measured in indoor dusts results more low than that found outside. The values of isomeric ratios for the differe…
Measurement of proton electromagnetic form factors in the time-like region using initial state radiation at BESIII
2021
Physics letters / B 817, 136328 (2021). doi:10.1016/j.physletb.2021.136328
Tevatron Combination of Single-Top-Quark Cross Sections and Determination of the Magnitude of the Cabibbo-Kobayashi-Maskawa Matrix Element Vtb
2015
et al.
Reconciling open charm production at the Fermilab Tevatron with QCD
2005
We study the inclusive hadrodroduction of D^0, D^+, D^{*+}, and D_s^+ mesons at next-to-leading order in the parton model of quantum chromodynamics endowed with universal non-perturbative fragmentation functions (FFs) fitted to e^+e^- annihilation data from CERN LEP1. Working in the general-mass variable-flavor-number scheme, we resum the large logarithms through the evolution of the FFs and, at the same time, retain the full dependence on the charm-quark mass without additional theoretical assumptions. In this way, the cross section distributions in transverse momentum recently measured by the CDF Collaboration in run II at the Fermilab Tevatron are described within errors.