Search results for "SII"
showing 10 items of 3468 documents
Soft-Dielectron Excess in Proton-Proton Collisions at √s = 13 TeV
2021
A measurement of dielectron production in proton-proton (pp) collisions at √s=13 TeV, recorded with the ALICE detector at the CERN LHC, is presented in this Letter. The data set was recorded with a reduced magnetic solenoid field. This enables the investigation of a kinematic domain at low dielectron (ee) invariant mass mee and pair transverse momentum pT,ee that was previously inaccessible at the LHC. The cross section for dielectron production is studied as a function of mee, pT,ee, and event multiplicity dNch/dη. The expected dielectron rate from hadron decays, called hadronic cocktail, utilizes a parametrization of the measured η/π0 ratio in pp and proton-nucleus collisions, assuming th…
p−p, p−Λ, and Λ−Λ correlations studied via femtoscopy in pp reactions at √s = 7 TeV
2019
We report on the first femtoscopic measurement of baryon pairs, such as p−p, p−Λ, and Λ−Λ, measured by ALICE at the Large Hadron Collider (LHC) in proton-proton collisions at √s=7 TeV. This study demonstrates the feasibility of such measurements in pp collisions at ultrarelativistic energies. The femtoscopy method is employed to constrain the hyperon-nucleon and hyperon-hyperon interactions, which are still rather poorly understood. A new method to evaluate the influence of residual correlations induced by the decays of resonances and experimental impurities is hereby presented. The p−p, p−Λ, and Λ−Λ correlation functions were fitted simultaneously with the help of a new tool developed spec…
Measurement of the 2+→0+ ground-state transition in the β decay of 20F
2019
We report the first detection of the second-forbidden, nonunique, 2+→0+, ground-state transition in the β decay of 20F. A low-energy, mass-separated 20F+ beam produced at the IGISOL facility in Jyväskylä, Finland, was implanted in a thin carbon foil and the β spectrum measured using a magnetic transporter and a plastic-scintillator detector. The β-decay branching ratio inferred from the measurement is bβ=[0.41±0.08(stat)±0.07(sys)]×10−5 corresponding to logft=10.89(11), making this one of the strongest second-forbidden, nonunique β transitions ever measured. The experimental result is supported by shell-model calculations and has significant implications for the final evolution of stars tha…
Measurement of prompt Ds+-meson production and azimuthal anisotropy in Pb–Pb collisions at √sNN = 5.02 TeV
2022
The production yield and angular anisotropy of prompt Ds+ mesons were measured as a function of transverse momentum (pT) in Pb–Pb collisions at a centre-of-mass energy per nucleon pair sNN=5.02TeV collected with the ALICE detector at the LHC. Ds+ mesons and their charge conjugates were reconstructed at midrapidity (|y|10GeV/c, the measured Ds+-meson nuclear modification factor RAA is consistent with the one of non-strange D mesons within uncertainties, while at lower pT a hint for a Ds+-meson RAA larger than that of non-strange D mesons is seen. The enhanced production of Ds+ relative to non-strange D mesons is also studied by comparing the pT-dependent Ds+/D0 production yield ratios in Pb–…
Transverse-momentum and event-shape dependence of D-meson flow harmonics in Pb–Pb collisions at √sNN = 5.02 TeV
2021
The elliptic and triangular flow coefficients v2 and v3 of prompt D0, D+, and D⁎+ mesons were measured at midrapidity (|y|<0.8) in Pb–Pb collisions at the centre-of-mass energy per nucleon pair of √sNN=5.02TeV with the ALICE detector at the LHC. The D mesons were reconstructed via their hadronic decays in the transverse momentum interval 1<36GeV/c in central (0–10%) and semi-central (30–50%) collisions. Compared to pions, protons, and J/ψ mesons, the average D-meson vn harmonics are compatible within uncertainties with a mass hierarchy for pT≲3GeV/c, and are similar to those of charged pions for higher pT. The coupling of the charm quark to the light quarks in the underlying medium is furth…
Quenching of the weak axial-vector coupling strength in β decays
2018
The quenching of the weak axial-vector coupling strength, gA, in nuclear β decays is reviewed. The quenching is discussed for both the Gamow–Teller decays and the forbidden β decays of different variants. Both the historical background and the present status are reviewed and compared with each other. Possible new measurements are urged, whenever relevant for determining the amount of gA quenching. peerReviewed
Elliptic Flow of Electrons from Beauty-Hadron Decays in Pb-Pb Collisions at √sNN = 5.02 TeV
2021
The elliptic flow of electrons from beauty hadron decays at midrapidity (|y|<0.8) is measured in Pb-Pb collisions at √sNN=5.02 TeV with the ALICE detector at the LHC. The azimuthal distribution of the particles produced in the collisions can be parametrized with a Fourier expansion, in which the second harmonic coefficient represents the elliptic flow, v2. The v2 coefficient of electrons from beauty hadron decays is measured for the first time in the transverse momentum (pT) range 1.3–6 GeV/c in the centrality class 30%–50%. The measurement of electrons from beauty-hadron decays exploits their larger mean proper decay length cτ≈500 μm compared to that of charm hadrons and most of the other …
FCC Physics Opportunities : Future Circular Collider Conceptual Design Report Volume 1
2019
We review the physics opportunities of the Future Circular Collider, covering its e+e-, pp, ep and heavy ion programmes. We describe the measurement capabilities of each FCC component, addressing the study of electroweak, Higgs and strong interactions, the top quark and flavour, as well as phenomena beyond the Standard Model. We highlight the synergy and complementarity of the different colliders, which will contribute to a uniquely coherent and ambitious research programme, providing an unmatchable combination of precision and sensitivity to new physics. peerReviewed
Measurement of charged pion double spin asymmetries at midrapidity in longitudinally polarized p+p collisions at √s = 510 GeV
2020
The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the longitudinal double spin asymmetries, A(LL), for charged pions at midrapidity (vertical bar eta vertical bar < 0.35) in longitudinally polarized p + p collisions at root s. = 510 GeV. These measurements are sensitive to the gluon spin contribution to the total spin of the proton in the parton momentum fraction x range between 0.04 and 0.09. One can infer the sign of the gluon polarization from the ordering of pion asymmetries with charge alone. The asymmetries are found to be consistent with global quantum-chromodynamics fits of deep-inelastic scattering and data at root s = 200 GeV, which show a nonzero positive …
Λc+ production in pp and in p-Pb collisions at √sNN = 5.02 TeV
2021
The production cross section of prompt Λ+c charm baryons was measured with the ALICE detector at the LHC at midrapidity in proton-proton (pp) and proton-lead (p–Pb) collisions at a center-of-mass energy per nucleon pair of √sNN = 5.02 TeV. The Λ+c and ¯Λ−c baryons were reconstructed in the hadronic decay channels Λ+c→pK−π+ and Λ+c→pK0S and respective charge conjugates. The measured differential cross sections as a function of transverse momentum (pT) and the pT-integrated Λ+c production cross section in pp and in p–Pb collisions are presented. The Λ+c nuclear modification factor (RpPb), calculated from the cross sections in pp and in p–Pb collisions, is presented and compared with the RpPb …