1,757 research outputs found
Investigating the p--π± and p--p--π± dynamics with femtoscopy in pp collisions at s=13 TeV
No full textThe interaction between pions and nucleons plays a crucial role in hadron physics. It represents a fundamental building block of the low-energy QCD dynamics and is subject to several resonance excitations. This work studies the p--π± dynamics using femtoscopic correlations in high-multiplicity pp collisions at s=13 TeV measured by ALICE at the LHC. As the final-state interaction between protons and pions is well constrained by scattering experiments and the study of pionic hydrogen, the results give access to information on the particle-emitting source in pp collisions using the femtoscopy methods. The scaling of the source size of primordial protons and pions against their pair transverse mass is extracted. The results are compared with the source sizes studied with p–p, p--K+, and π±–π± pairs by ALICE in the same collision system and are found to be in agreement for the different particle pairs. This reinforces recent findings by ALICE of a common emission source for all hadron-pairs in pp collisions at LHC energies. Furthermore, the p--p--π± systems are studied using three-particle femtoscopy in pp collisions at s=13 TeV. The presence of three-body effects is analyzed utilizing the cumulant expansion method. In this formalism, the known two-body interactions are subtracted in order to isolate the three-body effects. For both, p--p--π+ and p--p--π-, a non-zero cumulant is found, indicating effects beyond pairwise interactions. These results give information on the coupling of the pion to multiple nucleons
Search for B0(S) - anti-B0(S) oscillations in DELPHI using high-P(T) leptons.
Get PDFOscillations in the B-s(0)- [(B-s(0))over bar] system were studied in events selected from about 4.3 million hadronic Z(0) decays registered by DELPHI between 1992 and 2000. This paper presents updates of two published analyses ([11, 12]). The first analysis, which utilizes leptons emitted with large momentum transverse to a jet, was improved by means of a better algorithm for the vertex reconstuction and a new algorithm for flavour-tagging at production time. The second analysis, which utilizes D-s-lepton events, was improved by optimizing the treatment of proper time resolution. No signal of B-s(0) oscillations was observed and limits on the mass difference between the physical B-s(0) states were obtained to be: Deltam(s) gt 8.0 ps-1 at the 95% C.L. with a sensitivity of Deltam(s)= 9.1 ps(-1) in the high p(t) lepton analysis and Deltam(s) gt 4.9 ps(-1) at the 95% C.L. with a sensitivity of Deltam(s)=8.6 ps(-1) in the D-s-lepton analysis. Previously published results on these analyses are superseded. The combination of these results with those obtained in other independent analyses previously performed in DELPHI (D-s- hadron, exclusive B-s(0), inclusive vertex) gives: Deltam(s) gt 8.5 ps(-1) at the 95% C.L. with a sensitivity of Deltam(s)=12.0 ps(-1
Multiplicity dependence of pi, K, and p production in pp collisions at root s=13 TeV
Get PDFThis paper presents the measurements of π±, K±, p and p¯¯¯ transverse momentum (pT) spectra as a function of charged-particle multiplicity density in proton–proton (pp) collisions at s√ = 13 TeV with the ALICE detector at the LHC. Such study allows us to isolate the center-of-mass energy dependence of light-flavour particle production. The measurements reported here cover a pT range from 0.1 to 20 GeV/c and are done in the rapidity interval |y|<0.5. The pT-differential particle ratios exhibit an evolution with multiplicity, similar to that observed in pp collisions at s√ = 7 TeV, which is qualitatively described by some of the hydrodynamical and pQCD-inspired models discussed in this paper. Furthermore, the pT-integrated hadron-to-pion yield ratios measured in pp collisions at two different center-of-mass energies are consistent when compared at similar multiplicities. This also extends to strange and multi-strange hadrons, suggesting that, at LHC energies, particle hadrochemistry scales with particle multiplicity the same way under different collision energies and colliding systems
Study of the p–p–K + and p–p–K - dynamics using the femtoscopy technique
Get PDFThe interactions of kaons (K) and antikaons (K ̄) with few nucleons (N) were studied so far using kaonic atom data and measurements of kaon production and interaction yields in nuclei. Some details of the three-body KNN and K ̄ NN dynamics are still not well understood, mainly due to the overlap with multi-nucleon interactions in nuclei. An alternative method to probe the dynamics of three-body systems with kaons is to study the final state interaction within triplet of particles emitted in pp collisions at the Large Hadron Collider, which are free from effects due to the presence of bound nucleons. This Letter reports the first femtoscopic study of p–p–K + and p–p–K - correlations measured in high-multiplicity pp collisions at s = 13 TeV by the ALICE Collaboration. The analysis shows that the measured p–p–K + and p–p–K - correlation functions can be interpreted in terms of pairwise interactions in the triplets, indicating that the dynamics of such systems is dominated by the two-body interactions without significant contributions from three-body effects or bound states
K S 0 - and (anti-) Λ -hadron correlations in pp collisions at s = 13 TeV
Get PDFAbstract Two-particle Azimuthal correlations are measured with the ALICE apparatus in pp collisions at s = 13 TeV to explore strangeness- and multiplicity-related effects in the fragmentation of jets and the transition regime between bulk and hard production, probed with the condition that a strange meson ( K S 0 ) or baryon ( Λ ) with transverse momentum p T > 3 GeV/ c is produced. Azimuthal correlations between kaons or Λ hyperons with other hadrons are presented at midrapidity for a broad range of the trigger ( 3 < p T trigg < 20 GeV/ c ) and associated particle p T (1 GeV/ c < p T assoc < p T trigg ), for minimum-bias events and as a function of the event multiplicity. The near- and away-side peak yields are compared for the case of either K S 0 or Λ ( Λ ¯ ) being the trigger particle with that of inclusive hadrons (a sample dominated by pions). In addition, the measurements are compared with predictions from PYTHIA 8 and EPOS LHC event generators
Measurement of (1520) production in pp collisions at = 7 TeV and p-Pb collisions at = 5.02 TeV
No full textThe production of the (1520) baryonic resonance has been measured at midrapidity in inelastic pp collisions at = 7 TeV and in p-Pb collisions at = 5.02 TeV for non-single diffractive events and in multiplicity classes. The resonance is reconstructed through its hadronic decay channel (1520) pK and the charge conjugate with the ALICE detector. The integrated yields and mean transverse momenta are calculated from the measured transverse momentum distributions in pp and p-Pb collisions. The mean transverse momenta follow mass ordering as previously observed for other hyperons in the same collision systems. A Blast-Wave function constrained by other light hadrons (, K, K, p, ) describes the shape of the (1520) transverse momentum distribution up to 3.5 GeV/ in p-Pb collisions. In the framework of this model, this observation suggests that the (1520) resonance participates in the same collective radial flow as other light hadrons. The ratio of the yield of to the yield of the ground state particle remains constant as a function of charged-particle multiplicity, suggesting that there is no net effect of the hadronic phase in p-Pb collisions on the (1520) yield.The production of the (1520) baryonic resonance has been measured at midrapidity in inelastic pp collisions at and in p–Pb collisions at for non-single diffractive events and in multiplicity classes. The resonance is reconstructed through its hadronic decay channel (1520) and the charge conjugate with the ALICE detector. The integrated yields and mean transverse momenta are calculated from the measured transverse momentum distributions in pp and p–Pb collisions. The mean transverse momenta follow mass ordering as previously observed for other hyperons in the same collision systems. A Blast-Wave function constrained by other light hadrons (, K, , p, ) describes the shape of the (1520) transverse momentum distribution up to in p–Pb collisions. In the framework of this model, this observation suggests that the (1520) resonance participates in the same collective radial flow as other light hadrons. The ratio of the yield of to the yield of the ground state particle remains constant as a function of charged-particle multiplicity, suggesting that there is no net effect of the hadronic phase in p–Pb collisions on the (1520) yield.The production of the (1520) baryonic resonance has been measured at midrapidity in inelastic pp collisions at = 7 TeV and in p-Pb collisions at = 5.02 TeV for non-single diffractive events and in multiplicity classes. The resonance is reconstructed through its hadronic decay channel (1520) pK and the charge conjugate with the ALICE detector. The integrated yields and mean transverse momenta are calculated from the measured transverse momentum distributions in pp and p-Pb collisions. The mean transverse momenta follow mass ordering as previously observed for other hyperons in the same collision systems. A Blast-Wave function constrained by other light hadrons (, K, K, p, ) describes the shape of the (1520) transverse momentum distribution up to 3.5 GeV/ in p-Pb collisions. In the framework of this model, this observation suggests that the resonance participates in the same collective radial flow as other light hadrons. The ratio of the yield of to the yield of the ground state particle remains constant as a function of charged-particle multiplicity, suggesting that there is no net effect of the hadronic phase in p-Pb collisions on the (1520) yield
Towards the understanding of the genuine three-body interaction for p-p-p and p-p-Lambda
No full textThree-body nuclear forces play an important role in the structure of nuclei and hypernuclei and are also incorporated in models to describe the dynamics of dense baryonic matter, such as in neutron stars. So far, only indirect measurements anchored to the binding energies of nuclei can be used to constrain the three-nucleon force, and if hyperons are considered, the scarce data on hypernuclei impose only weak constraints on the three-body forces. In this work, we present the first direct measurement of the p–p–p and p–p– Λ systems in terms of three-particle correlation functions carried out for pp collisions at s=13 TeV. Three-particle cumulants are extracted from the correlation functions by applying the Kubo formalism, where the three-particle interaction contribution to these correlations can be isolated after subtracting the known two-body interaction terms. A negative cumulant is found for the p–p–p system, hinting to the presence of a residual three-body effect while for p–p– Λ the cumulant is consistent with zero. This measurement demonstrates the accessibility of three-baryon correlations at the LHC
Study of the p–p–K and p–p–K dynamics using the femtoscopy technique
Get PDFThe interactions of kaons (K) and antikaons (K)
with few nucleons (N) were studied so far using kaonic
atom data and measurements of kaon production and interaction yields in nuclei. Some details of the three-body KNN
and KNN dynamics are still not well understood, mainly
due to the overlap with multi-nucleon interactions in nuclei.
An alternative method to probe the dynamics of three-body
systems with kaons is to study the final state interaction
within triplet of particles emitted in pp collisions at the Large
Hadron Collider, which are free from effects due to the presence of bound nucleons. This Letter reports the first femtoscopic study of p–p–K+ and p–p–K− correlations measured in high-multiplicity pp collisions at √s = 13 TeV
by the ALICE Collaboration. The analysis shows that the
measured p–p–K+ and p–p–K− correlation functions can be
interpreted in terms of pairwise interactions in the triplets,
indicating that the dynamics of such systems is dominated
by the two-body interactions without significant contributions from three-body effects or bound states
One-dimensional charged kaon femtoscopy in p-Pb collisions at root s(NN)=5.02 TeV
Get PDFThe correlations of identical charged kaons were measured in p-Pb collisions at √sNN = 5.02 TeV by the ALICE experiment at the LHC. The femtoscopic invariant radii and correlation strengths were extracted from one-dimensional kaon correlation functions and were compared with those obtained in pp and Pb-Pb collisions at √s = 7 TeV and √sNN = 2.76 TeV, respectively. The presented results also complement the identical-pion femtoscopic data published by the ALICE collaboration. The extracted radii increase with increasing charged- particle multiplicity and decrease with increasing pair transverse momentum. At comparable multiplicities, the radii measured in p-Pb collisions are found to be close to those observed in pp collisions. The obtained femtoscopic parameters are reproduced by the EPOS 3 hadronic interaction model and disfavor models with large initial size or strong collective expansion at low multiplicities
W and Z boson production in p-Pb collisions at TeV root s(NN)=5.02 TeV
No full textThe W and Z boson production was measured via the muonic decay channel
in proton-lead collisions at root s(NN) = 5.02 TeV at the Large Hadron
Collider with the ALICE detector. The measurement covers backward (4.46
< y(cms) < 2.96) and forward (2.03 < y(cms) < 3.53) rapidity regions,
corresponding to Pb-going and p-going directions, respectively. The
Z-boson production cross section, with dimuon invariant mass of 60 <
m(mu mu) < 120 GeV/c(2) and muon transverse momentum (p(T)(mu)) larger
than 20 GeV/c, is measured. The production cross section and charge
asymmetry of muons from W-boson decays with p(T)(mu) > 10 GeV/c are
determined. The results are compared to theoretical calculations both
with and without including the nuclear modification of the parton
distribution functions. The W-boson production is also studied as a
function of the collision centrality: the cross section of muons from
W-boson decays is found to scale with the average number of binary
nucleon-nucleon collisions within uncertainties
- …
