Kaon and Phi Production in Pion-Nucleus Reactions at 1.7 GeV/<i>c</i>

Wirth, J.

doi:10.1051/epjconf/201817113002

Cited by 3 publications

(3 citation statements)

References 11 publications

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“…In order to define a reference value in which no nuclear absorption is present, a double ratio (K − /K + ) W /(K − /K + ) C constructed from elementary π − N reactions by tak- ing into account the proper number of neutrons and protons in tungsten and carbon. This procedure results in a value of 0.93 ± 0.09 [40]. The fact that the measured double ratios are well below this reference demonstrates the K − absorption.…”

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confidence: 61%

“…The (anti-)kaon yield was extracted by fitting the measured mass distributions (examples in panels (a) and (b) in Fig. 1) obtained for the different p T − y (p − θ) intervals [40]. The Further, the obtained doubledifferential yields of K + and K − were corrected for reconstruction efficiency within the geometrical acceptance (≈ 12 − 30% for K + and ≈ 10 − 26% for K − ) and normalized to the total number of beam particles and the density of target atoms to obtain absolute cross-sections.…”

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confidence: 99%

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Strong absorption of hadrons with hidden and open strangeness in nuclear matter

Adamczewski-Musch,

Arnold,

Atomssa

et al. 2018

Preprint

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We present the first observation of K − and φ absorption within nuclear matter by means of π − -induced reactions on C and W targets at an incident beam momentum of 1.7 GeV/c studied with HADES at SIS18/GSI. The double ratio (K − /K + )W/(K − /K + )C is found to be 0.319 ± 0.009(stat) +0.014 −0.012 (syst) indicating a larger absorption of K − in heavier targets as compared to lighter ones. The measured φ/K − ratios in π − +C and π − +W reactions within the HADES acceptance are found to be equal to 0.55±0.03(stat) +0.06 −0.07 (syst) and to 0.63±0.05(stat) +0.11 −0.11 (syst), respectively. The similar ratios measured in the two different reactions demonstrate for the first time experimentally that the dynamics of the φ meson in nuclear medium is strongly coupled to the K − dynamics. The large difference in the φ production off C and W nuclei is discussed in terms of a strong φN in-medium coupling.

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confidence: 61%

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confidence: 99%

Strong absorption of hadrons with hidden and open strangeness in nuclear matter

Adamczewski-Musch,

Arnold,

Atomssa

et al. 2018

Preprint

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“…Due to the non-Gaussian fluctuations in the individual measurements, the resolution of the cumulative specific energy loss is improved by the truncated mean method, which excludes values beyond a 3σ window around the arithmetic mean. More information on the calibration of the drift chambers can be found in [251,321,322]. The particle identification for protons, deuterons and tritons is based on a combined measurement of time-of-flight and energy loss, as previously described.…”

Section: Specific Energy Loss In the Drift Chambersmentioning

confidence: 99%

Collective flow measurements in Gold-Gold collisions at 1.23 AGeV with HADES

Kardan

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In this thesis, the flow coefficients vn of the orders n = 1 − 6 are studied for protons and light nuclei in Au+Au collisions at Ebeam = 1.23 AGeV, equivalent to a center-of-mass energy in the nucleon-nucleon system of √sNN = 2.4 GeV. The detailed multi-differential measurement is performed with the HADES experiment at SIS18/GSI. HADES, with its large acceptance, covering almost full azimuth angle, combined with its high mass-resolution and good particle-identification capability, is well equipped to study the azimuthal flow pattern not only for protons, deuterons, and tritons but also for charged pions, kaons, the φ-mesons, electrons/positrons, as well as light nuclei like helions and alphas. The high statistics of more than seven billion Au-Au collisions recorded in April/May 2012 with HADES enables for the first time the measurement of higher order flow coefficients up to the 6th harmonic. Since the Fourier coefficient of 7th and 8th order are beyond the statistical significance only an upper bound is given. The Au+Au collision system is the largest reaction system with the highest particle multiplicities, which was measured so far with HADES. A dedicated correction method for the flow measurement had to be developed to cope with the reconstruction in-efficiencies due to occupancies of the detector system. The systematical bias of the flow measurement is studied and several sources of uncertainties identified, which mainly arise from the quality selection criteria applied to the analyzed tracks, the correction procedure for reconstruction inefficiencies, the procedures for particle identification (PID) and the effects of an azimuthally non-uniform detector acceptance. The systematic point-to-point uncertainties are determined separately for each particle type (proton, deuteron and triton), the order of the flow harmonics vn, and the centrality class. Further, the validity of the results is inspected in the range of their evaluated systematic uncertainties with several consistency checks. In order to enable meaningful comparisons between experimental observations and predictions of theoretical models, the classification of events should be well defined and in sufficiently narrow intervals of impact parameter. Part of this work included the implementation of the procedure to determine the centrality and orientation of the reaction. In the conclusion the experimental results are discussed, including various scaling properties of the flow harmonics. It is found that the ratio v4/v2 for protons and light nuclei (deuterons and tritons) at midrapidity for all centrality classes approaches values close to 0.5 at high transverse momenta, which was suggested to be indicative for an ideal hydrodynamic behaviour. A remarkable scaling is observed in the pt dependence of v2 (v4) at mid-rapidity of the three hydrogen isotopes, when dividing by their nuclear mass number A (A^2) and pt by A. This is consistent with naive expectations from nucleon coalescence, butraises the question whether this mass ordering can also be explained by a hydrodynamical-inspired approach, like the blast-wave model. The relation of v2 and v4 to the shape of the initial eccentricity of the collision system is studied. It is found that v2 is independent of centrality for all three particle species after dividing it by the averaged second order participant eccentricity v2/⟨ε2⟩. A similar scaling is shown for v4 after division by ⟨ε2⟩^2.

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