Bose–Einstein correlations in proton-proton collisions is an effective tool to study the space structure of the production amplitude. Usually rather simple parametrization of particle-emission ...distribution function has been used—exponential or Gaussian form. However if one consider a particle source as an expanding media the symmetric Levy distribution as the generalization exponential can be used. Then additional parameter—the index of stability—will appear. All parameters dependencies on the charged particle density and on the mean transverse momentum of the pion/hadron in the correlated pair are investigated.
Two scales in Bose–Einstein correlations Khoze, V. A.; Martin, A. D.; Ryskin, M. G. ...
European physical journal. C, Particles and fields,
04/2016, Letnik:
76, Številka:
4
Journal Article
Recenzirano
Odprti dostop
We argue that the secondaries produced in high-energy hadron collisions are emitted by small-size sources distributed over a much larger area in impact parameter space occupied by the interaction ...amplitude. That is, Bose–Einstein correlation of two emitted identical particles should be described by a ‘two-radii’ parametrisation ansatz. We discuss the expected energy, charged multiplicity and transverse momentum of the pair (that is,
s
,
N
ch
,
k
t
) behaviour of both the small and the large size components.
Bose–Einstein correlations of identical pions produced in high-energy pp collisions at the LHC allow a probe of the Pomeron exchange mechanism. The size of the domain which emits the pions depends on ...the multiplicity of events, but not on the collider energy. This confirms the universal structure of Pomeron exchange. The data at relatively low multiplicities indicate that the size of the source created by one-Pomeron exchange is much less than the size of the proton.
Bose-Einstein correlations in proton-proton collisions is an effective tool to study the space structure of the production amplitude. Usually rather simple parametrization of particle-emission ...distribution function has been used - exponential or gaussian form. However if one consider a particle source as an expanding media the symmetric Levy distribution as the generalization exponential can be used.Then additional parameter - the index of stability - will appear. All parameters dependencies on the charged particle density and on the mean transverse momentum of the pion/hadron in the correlated pair are investigated.
ATLAS measured the centrality dependence of the dijet yield using 165 nb-1 of p + Pb data collected at $\sqrt{^SNN}$ =8.16 TeV in 2016. The event centrality, which reflects the p+Pb impact parameter, ...is characterized by the total transverse energy registered in the Pb-going side of the forward calorimeter. The central-to-peripheral ratio of the scaled dijet yields, RCP, is evaluated, and the results are presented as a function of variables that reflect the kinematics of the initial hard parton scattering process. The RCP shows a scaling with the Bjorken x of the parton originating from the proton, xp, while no such trend is observed as a function of xPb. This analysis provides unique input to understanding the role of small proton spatial configurations in p + Pb collisions by covering parton momentum fractions from the valence region down to xp ~ 10-3 and xPb ~ 4 × 10-4.
A measurement of the mass of the Higgs boson combining the H → ZZ* → 4ℓ and H → γγ decay channels is presented. The result is based on 140 fb–1 of proton-proton collision data collected by the ATLAS ...detector during LHC run 2 at a centre-of-mass energy of 13 TeV combined with the run 1 ATLAS mass measurement, yielding a Higgs boson mass of 125.11 ± 0.09 (stat.) ± 0.06 (syst.) = 125.11 ± 0.11 GeV. This corresponds to a 0.09 % precision achieved on this fundamental parameter of the Standard Model of particle physics.
A search for a new pseudoscalar a-boson produced in events with a top-quark pair, where the a-boson decays into a pair of muons, is performed using $\sqrt{s}$=13 TeV pp collision data collected with ...the ATLAS detector at the LHC, corresponding to an integrated luminosity of 139 fb-1. The search targets the final state where only one top quark decays to an electron or muon, resulting in a signature with three leptons eμμ and μμμ. No significant excess of events above the Standard Model expectation is observed and upper limits are set on two signal models: $pp→t\bar{t}a$ and $pp→t\bar{t}$ with $t→H^±b, H^±→W^±a$, where $a→μμ$, in the mass ranges 15 GeV<ma<72 GeV and 120 GeV≤mH±≤160 GeV.
A key open question in the study of multiparticle production in high-energy pp collisions is the relationship between the “ridge”—i.e., the observed azimuthal correlations between particles in the ...underlying event that extend over all rapidities—and hard or semihard scattering processes. In particular, it is not known whether jets or their soft fragments are correlated with particles in the underlying event. To address this question, two-particle correlations are measured in pp collisions at $\sqrt{s}$=13 TeV using data collected by the ATLAS experiment at the LHC, with an integrated luminosity of 15.8 pb-1, in two different configurations. In the first case, charged particles associated with jets are excluded from the correlation analysis, while in the second case, correlations are measured between particles within jets and charged particles from the underlying event. Second-order flow coefficients, v2, are presented as a function of event multiplicity and transverse momentum. These measurements show that excluding particles associated with jets does not affect the measured correlations. Moreover, particles associated with jets do not exhibit any significant azimuthal correlations with the underlying event, ruling out hard processes contributing to the ridge.
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