The largely unknown parton distribution functions of nuclei and the similarities observed between high-multiplicity pp and pPb events compared to PbPb, often described by means of hydrodynamics, are ...the main motivations for an extended pPb data taking program during LHC Run 3 and Run 4. The future increase in luminosity combined with the LHCb unique detector capabilities will allow to perform new and precise measurements. Moreover, an upgraded internal gas target is going to be installed for the LHCb Run 3, allowing a wider choice of target gas species and an increase of the gas density by up to two orders of magnitude. Prospects will be presented on both the LHCb collider and fixed target programs.
Abstract
Particle identification at high-energy physics experiments typically relies on classifiers combining different experimental observables. In this document, an innovative approach employing ...machine learning techniques to describe their dependence from the relevant features is presented. The proposed method is applied to the fixed-target programme at the LHCb experiment, where the sample size of the particle identification calibration channels affects the experimental performance. It is demonstrated to perform better than a model based on the LHCb detailed simulation and to be fast and suitable to a large variety of use cases.
A
bstract
A comprehensive set of azimuthal single-spin and double-spin asymmetries in semi-inclusive leptoproduction of pions, charged kaons, protons, and antiprotons from transversely polarized ...protons is presented. These asymmetries include the previously published HERMES results on Collins and Sivers asymmetries, the analysis of which has been extended to include protons and antiprotons and also to an extraction in a three-dimensional kinematic binning and enlarged phase space. They are complemented by corresponding results for the remaining four single-spin and four double-spin asymmetries allowed in the one-photon-exchange approximation of the semi-inclusive deep-inelastic scattering process for target-polarization orientation perpendicular to the direction of the incoming lepton beam. Among those results, significant non-vanishing cos (
ϕ−ϕ
S
) modulations provide evidence for a sizable worm-gear (II) distribution,
g
1
T
q
x
p
T
2
. Most of the other modulations are found to be consistent with zero with the notable exception of large sin (
ϕ
S
) modulations for charged pions and
K
+
.
The LHCspin project Santimaria, Marco; Carassiti, Vittore; Ciullo, Giuseppe ...
SciPost physics proceedings,
07/2022
8
Journal Article
Recenzirano
Odprti dostop
Broad and unexplored kinematic regions can be accessed at the LHC
with fixed-target
pp
p
p
,
pA
p
A
and
PbA
P
b
A
collisions at
\sqrt{s_{NN}}
s
N
N
=72-115 GeV. The LHCb detector is a ...fully-instrumented
forward spectrometer able to run in fixed-target mode, and currently
hosts a target gas cell to take data in the upcoming Run 3. The LHCspin
project aims at extending this physics program to Run 4 and to bring
polarised physics at the LHC. An overview of the physics potential and a
description of the LHCspin experimental setup are presented.
The influence of the cold nuclear medium effects on hadron multiplicities in semiinclusive deepinelastic scattering was studied extensively. A series of measurements on deuterium, helium, neon, ...krypton and xenon target has been performed in order to study hadronization. Hadron multiplicities on nucleus A relative to those on deuteron are presented for various hadrons together with the first direct measurement of pt-broadening effects in lepto production. The data have been accumulated by the Hermes experiment at the Desy laboratory using a 27.6 GeV positron or electron beam. These analysis provide precious information concerning the spacetime evolution of hadronization.
Abstract
Conventional, hadronic matter consists of baryons and mesons made of three quarks and a quark–antiquark pair, respectively
1,2
. Here, we report the observation of a hadronic state ...containing four quarks in the Large Hadron Collider beauty experiment. This so-called tetraquark contains two charm quarks, a
$$\overline{{{u}}}$$
u
¯
and a
$$\overline{{{d}}}$$
d
¯
quark. This exotic state has a mass of approximately 3,875 MeV and manifests as a narrow peak in the mass spectrum of
D
0
D
0
π
+
mesons just below the
D
*+
D
0
mass threshold. The near-threshold mass together with the narrow width reveals the resonance nature of the state.
Results are reported from an amplitude analysis of the B+ → D+D− K+ decay. The analysis is carried out using LHCb proton-proton collision data taken at √s = 7, 8, and 13 TeV, corresponding to a total ...integrated luminosity of 9 fb−1. In order to obtain a good description of the data, it is found to be necessary to include new spin-0 and spin-1 resonances in the D−K+ channel with masses around 2.9 GeV/c2, and a new spin-0 charmonium resonance in proximity to the spin-2 χc2(3930) state.
At sufficiently high temperature and energy density, nuclear matter undergoes a transition to a phase in which quarks and gluons are not confined: the quark-gluon plasma (QGP). Such an exotic state ...of strongly interacting quantum chromodynamics matter is produced in the laboratory in heavy nuclei high-energy collisions, where an enhanced production of strange hadrons is observed. Strangeness enhancement, originally proposed as a signature of QGP formation in nuclear collisions, is more pronounced for multi-strange baryons. Several effects typical of heavy-ion phenomenology have been observed in high-multiplicity proton-proton (pp) collisions, but the enhanced production of multi-strange particles has not been reported so far. Here we present the first observation of strangeness enhancement in high-multiplicity proton-proton collisions. We find that the integrated yields of strange and multi-strange particles, relative to pions, increases significantly with the event charged-particle multiplicity. The measurements are in remarkable agreement with the p-Pb collision results, indicating that the phenomenon is related to the final system created in the collision. In high-multiplicity events strangeness production reaches values similar to those observed in Pb-Pb collisions, where a QGP is formed.