Engineering topics

Banerjee, D. (ORCID:0000000157437578)

Publications and source records attributed to Banerjee, D. (ORCID:0000000157437578).

6 records

DOE OSTI2025

Exclusive photoproduction of excited ρ mesons decaying to four pions in ultraperipheral Pb–Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV

The intense photon ﬂuxes from relativistic nuclei provide an opportunity to study photonuclear interactions in ultraperipheral collisions. In particular, it allows for the investigations of excited, light-ﬂavour vector mesons. The measurement of coherently photoproduced 𝜋⁺𝜋 − 𝜋⁺𝜋 − ﬁnal states in ultraperipheral Pb–Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV is presented for the ﬁrst time. The cross section, d𝜎/d𝑦, times the branching ratio (𝜌 → 𝜋⁺𝜋⁺𝜋 − 𝜋 − ) is found to be 47.8 ± 2.3 (stat.) ± 7.7 (syst.) mb in the rapidity interval |𝑦| < 0.5. The invariant mass distribution is not well described with a single Breit-Wigner resonance without an interference term. Including in- terference with a non-resonant contribution results in the mass and width values being too far from those reported in PDG, while the production of two interfering resonances, 𝜌(1450) and 𝜌(1700), also provides a good description of the data. The values of the masses (𝑚) and widths (Γ) of the resonances extracted from the ﬁt assuming two interfering resonances are 𝑚₁ = 1385 ± 14 (stat.) ± 3 (syst.) MeV/𝑐², Γ₁ = 431 ± 36 (stat.) ± 82 (syst.) MeV/𝑐², 𝑚₂ = 1663 ± 13 (stat.) ± 22 (syst.) MeV/𝑐² and Γ₂ = 357 ± 31 (stat.) ± 49 (syst.) MeV/𝑐², respectively. The measured cross sections times the branching ratios are compared to recent theoretical predictions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2025

First polarisation measurement of coherently photoproduced J/ ψ in ultra-peripheral Pb–Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV

The first measurement of the polarisation of coherently photoproduced J/ψ mesons in ultra-peripheral Pb–Pb collisions, using data at $\sqrt{s_{NN}}$ = 5.02 TeV, is presented. The J/ψ meson is measured via its dimuon decay channel in the forward rapidity interval –4.0 < y < –2.5 using the ALICE detector at the CERN LHC. An event sample corresponding to an integrated luminosity of 750 μb –1 ± 5% (syst) is analysed. Hadronic activity is highly suppressed since the interaction is mediated by a photon. The polar and azimuthal angle distributions of the decay muons are measured, and the polarisation parameters λ θ , λ φ , λ θφ , are extracted. The analysis is carried out in the helicity frame. The results are found to be consistent with a transversely polarised J/ψ. These values are compared with previous measurements by the H1 and ZEUS experiments. The polarisation parameters of coherent J/ψ photoproduction in Pb–Pb collisions are found to be consistent with the s-channel helicity conservation hypothesis.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Multiplicity dependence of ϒ production at forward rapidity in pp collisions at $\sqrt{s}$ = 13 TeV

The measurement of ϒ(1S), ϒ(2S), and ϒ(3S) yields as a function of the charged-particle multiplicity density, d N ch /d η , using the ALICE experiment at the LHC, is reported in pp collisions at √s = 13 TeV. The Υ meson yields are measured at forward rapidity (2.5 < y < 4) in the dimuon decay channel, whereas the charged-particle multiplicity is defined at central rapidity (| η | <1). Both quantities are divided by their average value in minimum bias events to compute the self-normalized quantities. The increase of the self-normalized ϒ(1S), ϒ(2S), and ϒ(3S) yields is found to be compatible with a linear scaling with the self-normalized d N ch /d η , within the uncertainties. The self-normalized yield ratios of excited-to-ground ϒ states are compatible with unity within uncertainties. Similarly, the measured double ratio of the self-normalized ϒ(1S) to the self-normalized J/ ψ yields, both measured at forward rapidity, is compatible with unity for self-normalized charged-particle multiplicities beyond one. The measurements are compared with theoretical predictions incorporating initial or final state effects.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Measurement of 3 Λ H production in Pb–Pb collisions at √ s NN = 5.02 TeV

The first measurement of 3 Λ H and $^{3}_{\overline{Λ}}$$\overline{H}$ differential production with respect to transverse momentum and centrality in Pb–Pb collisions at √ s NN = 5.02 TeV is presented. The 3 Λ H has been reconstructed via its two-charged-body decay channel, i.e., 3 Λ H → 3 He → π - . A Blast-Wave model fit of the p T -differential spectra of all nuclear species measured by the ALICE collaboration suggests that the kinetic freeze-out surface is consistent with that of other nuclei. The ratio between the integrated yields of 3 Λ H and 3 He is compared to predictions from the statistical hadronisation model and the coalescence model, with the latter being favoured by the presented measurements.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Charm fragmentation fractions and $\mathbf {c\overline{c}}$ cross section in p–Pb collisions at $\mathbf {\sqrt{s _{NN}}=5.02 TeV}$

The total charm-quark production cross section per unit of rapidity dσ($\mathbf {c\overline{c}}$)/dy, and the fragmentation fractions of charm quarks to different charm-hadron species f(c → h c ), are measured for the first time in p–Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV at midrapidity (–0.96 < y < 0.04 in the centre-of-mass frame) using data collected by ALICE at the CERN LHC. The results are obtained based on all the available measurements of prompt production of ground-state charm-hadron species: D 0 , D + , D$^{+}_{s}$, and J/ψ mesons, and Λ$^{+}_{c}$ and $Ξ$$^{0}_{c}$ baryons. The resulting cross section is dσ($\mathbf {c\overline{c}}$)/dy = 219.6 ± 6.3 (stat.) $^{+10.5}_{–11.8}$ (syst.) $^{+8.3}_{–2.9}$ (extr.) ± 5.4 (BR) ± 4.6 (lumi.) ± 19.5 (rapidity shape) + 15.0 (Ω$^{0}_{c}$) mb, which is consistent with a binary scaling of pQCD calculations from pp collisions. The measured fragmentation fractions are compatible with those measured in pp collisions at $\sqrt{s_{NN}}$ = 5.02 and 13 TeV, showing an increase in the relative production rates of charm baryons with respect to charm mesons in pp and p–Pb collisions compared with e + e – and e – p collisions. The p T -integrated nuclear modification factor of charm quarks, R pPb ($\mathbf {c\overline{c}}$) = 0.91 ± 0.04 (stat.) $^{+0.08}_{–0.09}$ (syst.) $^{+0.05}_{–0.03}$ (extr.) ± 0.03 (lumi.), is found to be consistent with unity and with theoretical predictions including nuclear modifications of the parton distribution functions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Rapidity dependence of antideuteron coalescence in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE

The production yields of antideuterons and antiprotons are measured in pp collisions at a center-of-mass energy of $\sqrt{s}$ = 13 TeV, as a function of transverse momentum ( p T ) and rapidity ( y ), for the first time rapidity-differentially up to | y | = 0.7. The measured spectra are used to study the p T and rapidity dependence of the coalescence parameter B 2 , which quantifies the coalescence probability of antideuterons. The p T and rapidity dependence of the obtained B 2 is extrapolated for p T > 1.7 GeV/ c and | y | = 0.7 using the phenomenological antideuteron production model implemented in Pythia 8.3 as well as a baryon coalescence afterburner model based on EPOS 3. Such measurements are of interest to the astrophysics community, since they can be used for the calculation of the flux of antinuclei from cosmic rays, in combination with coalescence models.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗