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Register a new userSearch for an exotic S=-2, Q=-2 baryon resonance in proton-proton interactions at $sqrt{s_{NN}}$ = 17.3 GeV
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Pentaquark states have been extensively investigated theoretically in the context of the constituent quark model. In this paper results of an experimental search for pentaquarks in the Ximpim, Ximpip, Xippim and Xippip invariant mass spectra in proton-proton interactions at $sqrt{s}$=17.3~GeV are presented. Previous possible evidence from the NA49 collaboration of the existence of a narrow Ximpim baryon resonance in p+p interactions is not confirmed with almost 10 times greater event statistics. The search was performed using the NASixtyOne detector which reuses the main components of the NA49 apparatus. No signal was observed with either the selection cuts of NA49 or newly optimised cuts.
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Results of resonance searches in the Xi- pi-, Xi- pi+, antiXi+ pi- and antiXi+ pi+ invariant mass spectra in proton-proton collisions at sqrt{s}=17.2 GeV are presented. Evidence is shown for the existence of a narrow Xi- pi- baryon resonance with mass of 1.862+/-0.002 GeV/c^2 and width below the detector resolution of about 0.018 GeV/c^2. The significance is estimated to be 4.0 sigma. This state is a candidate for the hypothetical exotic Xi_(3/2)^-- baryon with S = -2, I = 3/2 and a quark content of (d s d s ubar). At the same mass a peak is observed in the Xi- pi+ spectrum which is a candidate for the Xi_(3/2)^0 member of this isospin quartet with a quark content of (d s u s dbar). The corresponding antibaryon spectra also show enhancements at the same invariant mass.
The momentum correlation between protons and lambda particles emitted from central Pb+Pb collisions at sqrt(s_{NN}) = 17.3 GeV was studied by the NA49 experiment at the CERN SPS. A clear enhancement is observed for small relative momenta (q_{inv} < 0.2 GeV). By fitting a theoretical model, which uses the strong interaction between the proton and the lambda in a given pair, to the measured data a value for the effective source size is deduced. Assuming a static Gaussian source distribution we derive an effective radius parameter of R_G = 3.02 pm 0.20$(stat.)^{+0.44}_{-0.16}(syst.) fm.
The production of $Xi(1321)^{-}$ and $overline{Xi}(1321)^{+}$ hyperons in inelastic p+p interactions is studied in a fixed target experiment at a beam momentum of 158 GeV/textit{c}. Double differential distributions in rapidity y and transverse momentum $p_{T}$ are obtained from a sample of 33M inelastic events. They allow to extrapolate the spectra to full phase space and to determine the mean multiplicity of both $Xi^{-}$ and $overline{Xi}^{+}$. The rapidity and transverse momentum spectra are compared to transport model predictions. The $Xi^{-}$ mean multiplicity in inelastic p+p interactions at 158~GeVc is used to quantify the strangeness enhancement in A+A collisions at the same centre-of-mass energy per nucleon pair.
Double-differential yields of $Xileft(1530right)^{0}$ and $overline{Xi}left(1530right)^{0}$ resonances produced in pp interactions were measured at a laboratory beam momentum of 158~GeVc. This measurement is the first of its kind in pp interactions below LHC energies. It was performed at the CERN SPS by the NASixtyOne collaboration. Double-differential distributions in rapidity and transverse momentum were obtained from a sample of 26$cdot$10$^6$ inelastic events. The spectra are extrapolated to full phase space resulting in mean multiplicity of $Xileft(1530right)^{0}$ (6.73 $pm$ 0.25 $pm$ 0.67)$times10^{-4}$ and $overline{Xi}left(1530right)^{0}$ (2.71 $pm$ 0.18 $pm$ 0.18)$times10^{-4}$. The rapidity and transverse momentum spectra and mean multiplicities were compared to predictions of string-hadronic and statistical model calculations.
We report on a search for elementary particles with charges much smaller than the electron charge using a data sample of proton-proton collisions provided by the CERN Large Hadron Collider in 2018, corresponding to an integrated luminosity of 37.5 fb$^{-1}$ at a center-of-mass energy of 13 TeV. A prototype scintillator-based detector is deployed to conduct the first search at a hadron collider sensitive to particles with charges ${leq}0.1e$. The existence of new particles with masses between 20 and 4700 MeV is excluded at 95% confidence level for charges between $0.006e$ and $0.3e$, depending on their mass. New sensitivity is achieved for masses larger than $700$ MeV.
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