The prompt production of the charm baryon Λ+c and the Λ+c/D0 production ratios were measured at midrapidity with the ALICE detector in pp and p-Pb collisions at √sNN=5.02 TeV. These new measurements ...show a clear decrease of the Λ+c/D0 ratio with increasing transverse momentum (pT) in both collision systems in the range 2<pT<12 GeV/c, exhibiting similarities with the light-flavor baryon-to-meson ratios p/π and Λ/K0S. At low pT, predictions that include additional color-reconnection mechanisms beyond the leading-color approximation, assume the existence of additional higher-mass charm-baryon states, or include hadronization via coalescence can describe the data, while predictions driven by charm-quark fragmentation processes measured in e+e− and e−p collisions significantly underestimate the data. The results presented in this Letter provide significant evidence that the established assumption of universality (colliding-system independence) of parton-to-hadron fragmentation is not sufficient to describe charm-baryon production in hadronic collisions at LHC energies.
The production of K*(892)0 and $\phi$(1020) resonances has been measured in p-Pb collisions at $\sqrt{s_{NN}}$ = 8.16 TeV using the ALICE detector. Resonances are reconstructed via their hadronic ...decay channels in the rapidity interval -0.5 < y < 0 and the transverse momentum spectra are measured for various multiplicity classes up to pT = 20 GeV/c for K*(892)0 and pT = 16 GeV/c for $\phi$(1020). The pT-integrated yields and mean transverse momenta are reported and compared with previous results in pp, p-Pb and Pb-Pb collisions. The xT scaling for K*(892)0 and $\phi$(1020) resonance production is newly tested in p-Pb collisions and found to hold in the high-pT region at Large Hadron Collider energies. The nuclear modification factors (RpPb) as a function of pT for K*0 and $\phi$ at $\sqrt{s_{NN}}$ = 8.16 TeV are presented along with the new RpPb measurements of K*0, $\phi$, Ξ, and Ω at $\sqrt{s_{NN}}$ = 5.02 TeV. At intermediate pT (2–8 GeV/c), RpPb of Ξ, Ω show a Cronin-like enhancement, while K*0 and $\phi$ show no or little nuclear modification. At high pT (>8 GeV/c), the RpPb values of all hadrons are consistent with unity within uncertainties. The RpPb of K*(892)0 and $\phi$(1020) at $\sqrt{s_{NN}}$ = 8.16 and 5.02 TeV show no significant energy dependence.
Microplastics and its putative adverse effects on environmental and human health increasingly gain scientific and public attention. Systematic studies on the effects of microplastics are currently ...hampered by using rather poorly characterised particles, leading to contradictory results for the same particle type. Here, surface properties and chemical composition of two commercially available nominally identical polystyrene microparticles, frequently used in effect studies, were characterised. We show distinct differences in monomer content, ζ-potentials and surface charge densities. Cells exposed to particles showing a lower ζ-potential and a higher monomer content displayed a higher number of particle-cell-interactions and consequently a decrease in cell metabolism and proliferation, especially at higher particle concentrations. Our study emphasises that no general statements can be made about the effects of microplastics, not even for the same polymer type in the same size class, unless the physicochemical properties are well characterised.
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•Supposedly identical particles from different sources tremendously differ in their properties.•Different properties lead to significant differences in particle-cell interactions and cytotoxicity.•In-depth material characterisation of microplastics is needed to obtain comparable results.•No general statement can be made about effects of microplastics per se, not even for the same polymer type in the same size.
Reconstitution of the T cell repertoire after allogeneic stem cell transplantation is a long and often incomplete process. As a result, reactivation of Epstein-Barr virus (EBV) is a frequent ...complication that may be treated by adoptive transfer of donor-derived EBV-specific T cells. We generated donor-derived EBV-specific T cells by stimulation with peptides representing defined epitopes covering multiple HLA restrictions. T cells were adoptively transferred to a patient who had developed persisting high titers of EBV after allogeneic stem cell transplantation for angioimmunoblastic T-cell lymphoma (AITL). T cell receptor beta (TCRβ) deep sequencing showed that the T cell repertoire of the patient early after transplantation (day 60) was strongly reduced and only very low numbers of EBV-specific T cells were detectable. Manufacturing and in vitro expansion of donor-derived EBV-specific T cells resulted in enrichment of EBV epitope-specific, HLA-restricted T cells. Monitoring of T cell clonotypes at a molecular level after adoptive transfer revealed that the dominant TCR sequences from peptide-stimulated T cells persisted long-term and established an EBV-specific TCR clonotype repertoire in the host, with many of the EBV-specific TCRs present in the donor. This reconstituted repertoire was associated with immunological control of EBV and with lack of further AITL relapse.
The production cross section of prompt Λc+ charm baryons was measured with the ALICE detector at the LHC at midrapidity in proton-proton (pp) and proton-lead (p-Pb) collisions at a center-of-mass ...energy per nucleon pair of sNN=5.02TeV. The Λc+ and Λ¯c- baryons were reconstructed in the hadronic decay channels Λc+→pK-π+ and Λc+→pKS0 and respective charge conjugates. The measured differential cross sections as a function of transverse momentum (pT) and the pT-integrated Λc+ production cross section in pp and in p-Pb collisions are presented. The Λc+ nuclear modification factor (RpPb), calculated from the cross sections in pp and in p-Pb collisions, is presented and compared with the RpPb of D mesons. The Λc+/D0 ratio is also presented and compared with the light-flavor baryon-to-meson ratios p/π and Λ/KS0, and measurements from other LHC experiments. The results are compared to predictions from model calculations and Monte Carlo event generators.
A
bstract
We present the measurement of a new set of jet shape observables for track-based jets in central Pb-Pb collisions at
s
N
N
=
2.76
TeV. The set of jet shapes includes the first radial moment ...or angularity,
g
; the momentum dispersion,
p
T
D
; and the difference between the leading and sub-leading constituent track transverse momentum,
LeSub
. These observables provide complementary information on the jet fragmentation and can constrain different aspects of the theoretical description of jet-medium interactions. The jet shapes were measured for a small resolution parameter
R
= 0
.
2 and were fully corrected to particle level. The observed jet shape modifications indicate that in-medium fragmentation is harder and more collimated than vacuum fragmentation as obtained by PYTHIA calculations, which were validated with the measurements of the jet shapes in proton-proton collisions at
s
=
7
TeV. The comparison of the measured distributions to templates for quark and gluon-initiated jets indicates that in-medium fragmentation resembles that of quark jets in vacuum. We further argue that the observed modifications are not consistent with a totally coherent energy loss picture where the jet loses energy as a single colour charge, suggesting that the medium resolves the jet structure at the angular scales probed by our measurements (
R
= 0
.
2). Furthermore, we observe that small-
R
jets can help to isolate purely energy loss effects from other effects that contribute to the modifications of the jet shower in medium such as the correlated background or medium response.
The production yield of the Λ (1520) baryon resonance is measured at midrapidity in Pb-Pb collisions at s NN = 2.76 TeV with the ALICE detector at the Large Hadron Collider (LHC). The measurement is ...performed in the Λ (1520)→ p K - (and charge conjugate) hadronic decay channel as a function of the transverse momentum ( p T ) and collision centrality. The ratio of the p T -integrated production of Λ (1520) baryons relative to Λ baryons in central collisions is suppressed by about a factor of 2 with respect to peripheral collisions. This is the first observation of the suppression of a baryonic resonance at the LHC and the first 3σ evidence of Λ (1520) suppression within a single collision system. The measured Λ (1520)/ Λ ratio in central collisions is smaller than the value predicted by the statistical hadronization model calculations. The shape of the measured p T distribution and the centrality dependence of the suppression are reproduced by the EPOS3 Monte Carlo event generator. The measurement adds further support to the formation of a dense hadronic phase in the final stages of the evolution of the fireball created in heavy-ion collisions, lasting long enough to cause a significant reduction in the observable yield of short-lived resonances.
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