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    Exploring the N Lambda-N Lambda coupled system with high precision correlation techniques at the LHC
    (Cornell University, 2021-04-09)
    ELSEVIER RADARWEG 29, 1043 NX AMSTERDAM, NETHERLANDS
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    Measurement of anti-3He nuclei absorption in matter and impact on their propagation in the Galaxy
    (Nature Portfolio, 2022-12-12)
    In our Galaxy, light antinuclei composed of antiprotons and antineutrons can be produced through high-energy cosmic-ray collisions with the interstellar medium or could also originate from the annihilation of dark-matter particles that have not yet been discovered. On Earth, the only way to produce and study antinuclei with high precision is to create them at high-energy particle accelerators. Although the properties of elementary antiparticles have been studied in detail, the knowledge of the interaction of light antinuclei with matter is limited. We determine the disappearance probability of $${}^{3}\overline{{{{\rm{He}}}}}$$ 3 He ¯ when it encounters matter particles and annihilates or disintegrates within the ALICE detector at the Large Hadron Collider. We extract the inelastic interaction cross section, which is then used as an input to the calculations of the transparency of our Galaxy to the propagation of $${}^{3}\overline{{{{\rm{He}}}}}$$ 3 He ¯ stemming from dark-matter annihilation and cosmic-ray interactions within the interstellar medium. For a specific dark-matter profile, we estimate a transparency of about 50%, whereas it varies with increasing $${}^{3}\overline{{{{\rm{He}}}}}$$ 3 He ¯ momentum from 25% to 90% for cosmic-ray sources. The results indicate that $${}^{3}\overline{{{{\rm{He}}}}}$$ 3 He ¯ nuclei can travel long distances in the Galaxy, and can be used to study cosmic-ray interactions and dark-matter annihilation.
      1
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    Measurement of the fraction of jet longitudinal momentum carried by Λc+ baryons in pp collisions
    (American Physical Society, 2024-04-01)
    Recent measurements of charm-baryon production in hadronic collisions have questioned the universality of charm-quark fragmentation across different collision systems. In this work the fragmentation of charm quarks into charm baryons is probed, by presenting the first measurement of the longitudinal jet momentum fraction carried by Λc+ baryons, z∥ch, in hadronic collisions. The results are obtained in proton-proton (pp) collisions at s=13 TeV at the LHC, with Λc+ baryons and charged (track-based) jets reconstructed in the transverse momentum intervals of 3≤pTΛc+<15 GeV/c and 7≤pTjet ch<15 GeV/c, respectively. The z∥ch distribution is compared to a measurement of D0-tagged charged jets in pp collisions as well as to pythia 8 simulations. The data hints that the fragmentation of charm quarks into charm baryons is softer with respect to charm mesons, in the measured kinematic interval, as predicted by hadronization models which include color correlations beyond leading-color in the string formation.
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    Photoproduction of K+K− pairs in ultraperipheral collisions
    (American Physical Society, 2024-05-31)
    K+K- pairs may be produced in photonuclear collisions, either from the decays of photoproduced φ(1020) mesons or directly as nonresonant K+K- pairs. Measurements of K+K- photoproduction probe the couplings between the φ(1020) and charged kaons with photons and nuclear targets. The kaon-proton scattering occurs at energies far above those available elsewhere. We present the first measurement of coherent photoproduction of K+K- pairs on lead ions in ultraperipheral collisions using the ALICE detector, including the first investigation of direct K+K- production. There is significant K+K- production at low transverse momentum, consistent with coherent photoproduction on lead targets. In the mass range 1.1<MKK<1.4 GeV/c2 above the φ(1020) resonance, for rapidity |yKK|<0.8 and pT,KK<0.1 GeV/c, the measured coherent photoproduction cross section is dσ/dy=3.37±0.61(stat)±0.15(syst) mb. The center-of-mass energy per nucleon of the photon-nucleus (Pb) system WγPb,n ranges from 33 to 188 GeV, far higher than previous measurements on heavy-nucleus targets. The cross section is larger than expected for φ(1020) photoproduction alone. The mass spectrum is fit to a cocktail consisting of φ(1020) decays, direct K+K- photoproduction, and interference between the two. The confidence regions for the amplitude and relative phase angle for direct K+K- photoproduction are presented.
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    Multiplicity and Rapidity Dependence of K∗(892) and ϕ(1020) Production in p–Pb Collisions at √sNN = 5.02 TeV
    (Institute for Ionics, 2023-06-01)
    The transverse-momentum (pT) spectra of K ∗(892)0 and ϕ(1020) measured with the ALICE detector up to pT = 16 GeV/c in the rapidity range - 1.2 < y< 0.3 , in p–Pb collisions at the center-of-mass energy per nucleon–nucleon collision sNN=5.02 TeV are presented as a function of charged particle multiplicity and rapidity. The measured pT distributions show a dependence on both multiplicity and rapidity at low pT whereas no significant dependence is observed at high pT . A rapidity dependence is observed in the pT -integrated yield (dN/dy), whereas the mean transverse momentum (⟨ pT⟩) shows a flat behavior as a function of rapidity. The rapidity asymmetry (Yasym) at low pT (< 5 GeV/c) is more significant for higher multiplicity classes. At high pT , no significant rapidity asymmetry is observed in any of the multiplicity classes. Both K ∗(892)0 and ϕ(1020) show similar Yasym . The nuclear modification factor (QCP) as a function of pT shows a Cronin-like enhancement at intermediate pT , which is more prominent at higher rapidities (Pb-going direction) and in higher multiplicity classes. At high pT (> 5 GeV/ c), the QCP values are greater than unity and no significant rapidity dependence is observed.
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    Inclusive Photon Production at Forward Rapidities in pp and p–Pb Collisions at √sNN = 5.02 TeV
    (Institute for Ionics, 2023-07-01)
    A study of multiplicity and pseudorapidity distributions of inclusive photons measured in pp and p–Pb collisions at a center-of-mass energy per nucleon–nucleon collision of sNN=5.02 TeV using the ALICE detector in the forward pseudorapidity region 2.3 <ηlab< 3.9 is presented. Measurements in p–Pb collisions are reported for two beam configurations in which the directions of the proton and lead ion beam were reversed. The pseudorapidity distributions in p–Pb collisions are obtained for seven centrality classes which are defined based on different event activity estimators, i.e., the charged-particle multiplicity measured at midrapidity as well as the energy deposited in a calorimeter at beam rapidity. The inclusive photon multiplicity distributions for both pp and p–Pb collisions are described by double negative binomial distributions. The pseudorapidity distributions of inclusive photons are compared to those of charged particles at midrapidity in pp collisions and for different centrality classes in p–Pb collisions. The results are compared to predictions from various Monte Carlo event generators. None of the generators considered in this paper reproduces the inclusive photon multiplicity distributions in the reported multiplicity range. The pseudorapidity distributions are, however, better described by the same generators.
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    D0-meson-tagged jet axes difference in proton-proton collisions at √s = 5.02 TeV
    (American Physical Society, 2025-01-01)
    Heavy-flavor quarks produced in proton-proton (pp) collisions provide a unique opportunity to investigate the evolution of quark-initiated parton showers from initial hard scatterings to final-state hadrons. By examining jets that contain heavy-flavor hadrons, this study explores the effects of both perturbative and nonperturbative QCD on jet formation and structure. The angular differences between various jet axes, <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi mathvariant="normal">Δ</a:mi> <a:msub> <a:mi>R</a:mi> <a:mrow> <a:mi>axis</a:mi> </a:mrow> </a:msub> </a:math> , offer insight into the radiation patterns and fragmentation of charm quarks. The first measurement of <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"> <d:msup> <d:mi>D</d:mi> <d:mn>0</d:mn> </d:msup> </d:math> -tagged jet axes differences in pp collisions at <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"> <f:msqrt> <f:mi>s</f:mi> </f:msqrt> <f:mo>=</f:mo> <f:mn>5.02</f:mn> <f:mtext> </f:mtext> <f:mtext> </f:mtext> <f:mi>TeV</f:mi> </f:math> by the ALICE experiment at the LHC is presented for jets with transverse momentum <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"> <h:msubsup> <h:mi>p</h:mi> <h:mi mathvariant="normal">T</h:mi> <h:mtext>ch jet</h:mtext> </h:msubsup> <h:mo>≥</h:mo> <h:mn>10</h:mn> <h:mtext> </h:mtext> <h:mtext> </h:mtext> <h:mi>GeV</h:mi> <h:mo>/</h:mo> <h:mi>c</h:mi> </h:math> and <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"> <k:msup> <k:mi>D</k:mi> <k:mn>0</k:mn> </k:msup> </k:math> mesons with <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"> <m:mrow> <m:msubsup> <m:mrow> <m:mi>p</m:mi> </m:mrow> <m:mrow> <m:mi mathvariant="normal">T</m:mi> </m:mrow> <m:mrow> <m:msup> <m:mrow> <m:mi mathvariant="normal">D</m:mi> </m:mrow> <m:mrow> <m:mn>0</m:mn> </m:mrow> </m:msup> </m:mrow> </m:msubsup> <m:mo>≥</m:mo> <m:mn>5</m:mn> <m:mtext> </m:mtext> <m:mtext> </m:mtext> <m:mi>GeV</m:mi> <m:mo>/</m:mo> <m:mi>c</m:mi> </m:mrow> </m:math> . In this <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"> <q:msup> <q:mi>D</q:mi> <q:mn>0</q:mn> </q:msup> </q:math> -meson-tagged jet measurement, three jet axis definitions, each with different sensitivities to soft, wide-angle radiation, are used: the standard axis, soft drop groomed axis, and winner-takes-all axis. Measurements of the radial distributions of <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"> <s:msup> <s:mi>D</s:mi> <s:mn>0</s:mn> </s:msup> </s:math> mesons with respect to the jet axes, <u:math xmlns:u="http://www.w3.org/1998/Math/MathML" display="inline"> <u:mrow> <u:mi mathvariant="normal">Δ</u:mi> <u:msub> <u:mrow> <u:mi>R</u:mi> </u:mrow> <u:mrow> <u:mrow> <u:mi>axis</u:mi> </u:mrow> <u:mtext>−</u:mtext> <u:msup> <u:mrow> <u:mi mathvariant="normal">D</u:mi> </u:mrow> <u:mrow> <u:mn>0</u:mn> </u:mrow> </u:msup> </u:mrow> </u:msub> </u:mrow> </u:math> , are reported, along with the angle, <y:math xmlns:y="http://www.w3.org/1998/Math/MathML" display="inline"> <y:mi mathvariant="normal">Δ</y:mi> <y:msub> <y:mi>R</y:mi> <y:mrow> <y:mi>axis</y:mi> </y:mrow> </y:msub> </y:math> , between the three jet axes. The <bb:math xmlns:bb="http://www.w3.org/1998/Math/MathML" display="inline"> <bb:msup> <bb:mi>D</bb:mi> <bb:mn>0</bb:mn> </bb:msup> </bb:math> meson emerges as the leading particle in these jets, closely aligning with the winner-takes-all axis and diverging from the standard jet axis. The results also examine how varying the sensitivity to soft radiation with grooming influences the orientation of the soft drop jet axis and uncover that charm-jet structure is more likely to survive grooming when the soft drop axis is further from the <db:math xmlns:db="http://www.w3.org/1998/Math/MathML" display="inline"> <db:msup> <db:mi>D</db:mi> <db:mn>0</db:mn> </db:msup> </db:math> direction, providing further evidence of the dead-cone effect recently measured by ALICE.
      3
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    Addendum: Dielectron production in proton-proton and proton-lead collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msqrt> <mml:msub> <mml:mi>s</mml:mi> <mml:mrow> <mml:mi>N</mml:mi> <mml:mi>N</mml:mi> </mml:mrow> </mml:msub> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>5.02</mml:mn> <mml:mspace width="0.16em"/> <mml:mi>TeV</mml:mi> </mml:mrow> </mml:math>
    (American Institute of Physics Inc., 2025-02-07)
    This is an addendum to the article “Dielectron production in proton-proton and proton-lead collisions at <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:msqrt> <a:msub> <a:mi>s</a:mi> <a:mi>NN</a:mi> </a:msub> </a:msqrt> <a:mo>=</a:mo> <a:mn>5.02</a:mn> <a:mspace width="0.16em"/> <a:mi>TeV</a:mi> </a:mrow> </a:math> ” published in ]. We update the extracted charm cross section at midrapidity given in Table III and Fig. 4 (left) of the original publication with the fragmentation fractions of charm quarks in <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"> <c:mrow> <c:mi>p</c:mi> <c:mi>p</c:mi> </c:mrow> </c:math> collisions published in ].
      6