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. ...
The 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.
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.
This Letter reports the observation of τ-lepton pair production in ultraperipheral lead-lead collisions, Pb+Pb→Pb(γγ→ττ)Pb, and constraints on the τ-lepton anomalous magnetic moment, aτ. The dataset ...corresponds to an integrated luminosity of 1.44 nb-1 of LHC Pb+Pb collisions at $\sqrt{s_{NN}}$ =5.02 TeV recorded by the ATLAS experiment in 2018. Selected events contain one muon from a τ-lepton decay, an electron or charged-particle track(s) from the other τ-lepton decay, little additional central-detector activity, and no forward neutrons. The γγ→ττ process is observed in Pb+Pb collisions with a significance exceeding 5 standard deviations, and a signal strength of μττ=1.03$^{+0.06}_{-0.05}$ assuming the Standard Model value for aτ. To measure aτ, a template fit to the muon transverse-momentum distribution from τ-lepton candidates is performed, using a dimuon (γγ→μμ) control sample to constrain systematic uncertainties. The observed 95% confidence-level interval for aτ is -0.057 < aτ < 0.024.
The vector-boson production cross-section for the Higgs boson decay in the H→WW*→eνμν channel is measured as a function of kinematic observables sensitive to the Higgs boson production and decay ...properties as well as integrated in a fiducial phase space. The analysis is performed using the proton-proton collision data collected by the ATLAS detector in Run 2 of the LHC at $\sqrt{s}$=13 TeV center-of-mass energy corresponding to an integrated luminosity of 139 fb-1. The different flavor final state is studied by selecting an electron and a muon originating from a pair of W bosons and compatible with the Higgs boson decay. The data are corrected for the effects of detector inefficiency and resolution, and the measurements are compared with different state-of-the-art theoretical predictions. The differential cross-sections are used to constrain anomalous interactions described by dimension-six operators in an Effective Field Theory.
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