Cancellation of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>σ</mml:mi></mml:math>meson in thermal models

Broniowski, Wojciech; Giacosa, Francesco; Begun, Viktor

doi:10.1103/physrevc.92.034905

Cited by 74 publications

(87 citation statements)

References 44 publications

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“…As pointed out in Ref. [22], the inclusion of this channel partly cancels the effect of the isospin I = 1/2 channel. This is expected since the phase shift in the I = 3/2 channel, and consequently the weight function B I=3/2 (M ), are negative, corresponding to a repulsive interaction.…”

Section: The Effect Of I = 3/2 Kπ Scatteringmentioning

confidence: 64%

Strangeness fluctuations fromK−πinteractions

Friman

Marczenko

et al. 2015

Phys. Rev. D

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Motivated by recent lattice QCD studies, we explore the effects of interactions on strangeness fluctuations in strongly interacting matter at finite temperature. We focus on S-wave Kπ scattering and discuss the role of the K * 0 (800) and K * (1430) resonances within the S-matrix formulation of thermodynamics. Using the empirical Kπ phase shifts as input, we find that the Kπ S-wave interactions provide part of the missing contribution to the strangeness susceptibility. Moreover, it is shown that the simplified treatment of the interactions in this channel, employed in the hadron resonance gas approach, leads to a systematic overestimate of the strangeness fluctuations. In particular, the HRG results for the strangeness and mixed strangeness-baryon number susceptibilities (χ SS and χ BS ) are clearly below those of the lattice, while the results for the thermodynamic pressure and the baryon number susceptibility are in good agreement.This motivates the search for hitherto unknown strange hadrons, which could reduce or eliminate this discrepancy. In the PDG database, there are around twenty unconfirmed states with a mass below 2.0 GeV. Although these are not established resonances, the interactions in the corresponding scattering channels may yield important contribution to thermodynamic quantities.More generally, a possible origin of the discrepancy is interaction strength in channels carrying net strangeness that so far have not been accounted for. Given the corresponding empirical scattering phase shifts, both confirmed and unconfirmed resonances as well as nonresonant interactions can be handled in a unified, modelindependent way, using the S-matrix approach of Ref. [3].The strange scalar channel, with the unconfirmed K * 0 (800) resonance, a.k.a. κ, is a prime candidate. Since the corresponding phase shifts for S-wave Kπ scattering are fairly well determined, this channel is well suited for the S-matrix approach. In addition, the counterpart of κ in the scalar-isoscalar channel, the f 0 (500), a.k.a. σ, though considered to be established [4], is unlike a typical resonance. Since the ππ S-wave phase shifts are known with reasonable accuracy, also this channel is a prime candidate for the S-matrix approach to thermodynamics. In this study we focus on the strange scalar channel and its contribution to strangeness susceptibilities.With the relatively low mass of the interaction strength in the κ channel, it potentially has a large impact on the thermodynamics, in particular on χ SS , owing to the moderate suppression by the Boltzmann factor. In Fig. 1, we illustrate the effect of the κ resonance on pressure and strangeness fluctuation within the HRG approach. For the PDG particle spectrum, we use only confirmed baryons (i.e. three and four star resonances) and established mesons. The contribution of κ to the thermodynamics is approximated by that of an ideal gas of zero-width mesons with mass m κ = 0.682 GeV and degeneracy four. Indeed, the inclusion of this single state improves the HRG result on χ SS dramatica...

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Section: The Effect Of I = 3/2 Kπ Scatteringmentioning

confidence: 64%

Strangeness fluctuations fromK−πinteractions

Friman

Marczenko

et al. 2015

Phys. Rev. D

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“…Some recent studies indicate that its effect is crucial in some particular observables regarding CSR [357], whereas the effect of the σ has also been shown to compensate largely with the isospin 2 channel for other observables like scalar susceptibilities [362] . Actually this cancellation between the isoscalar and isotensor channels in hadron resonance gases was already found in [363] and in view of the present parameters of 116 the f 0 (500) meson it has been suggested that the sigma meson should not be included in Hadron Resonance Gas models (unless the isotensor wave is included too), as long as one is interested in isospin-averaged observables [364]. Furthermore, if the sigma is implemented and the low energy part is important for a given observable, we have shown in previous sections that the simplest LσM, which is the model most widely used for this purposes, is insufficient to describe our present knowledge.…”

Section: The σ Meson and Chiral Symmetry Restorationmentioning

confidence: 99%

From controversy to precision on the sigma meson: A review on the status of the non-ordinary f0(500) resonance

2016

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The existence and properties of the sigma meson have been controversial for almost six decades, despite playing a central role in the spontaneous chiral symmetry of QCD or in the nucleonnucleon attraction. This controversy has also been fed by the strong indications that it is not an ordinary quark-antiquark meson. Here we review both the recent and old experimental data and the model independent dispersive formalisms which have provided precise determinations of its mass and width, finally settling the controversy and leading to its new name: f 0 (500). We then provide a rather conservative average of the most recent and advanced dispersive determinations of its pole position √ s σ = 449 +22−16 −i(275±12). In addition, after comprehensive introductions, we will review within the modern perspective of effective theories and dispersion theory, its relation to chiral symmetry, unitarization techniques, its quark mass dependence, popular models, as well as the recent strong evidence, obtained from the QCD 1/N c expansion or Regge theory, for its non ordinary nature in terms of quarks and gluons.

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“…The σ implemented as a Breit-Winger pole with M σ = 484 and Γ σ /2 = 255 MeV produces up to 5% of pions, while the truth contribution is −0.3%, see Fig. 5 (right) [31]. The absence of pions from the σ decays enhances all ratios to pions, compared to the results that were obtained in models with σ.…”

Section: Icnfp 2015mentioning

confidence: 63%

“…The attractive one is responsible for the emergence of the f 0 (500) resonance, however, the repulsive one cancels f 0 (500) until f 0 (980) takes over above the mass M ππ ∼ 0.85 GeV, see Ref. [31]. The cancellation happens on the level of the distribution function, therefore it is present in all isospin-averaged observables.…”

Section: Icnfp 2015mentioning

confidence: 98%

High temperature Bose-Einstein condensation

Begun

2016

EPJ Web Conf.

Self Cite

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Abstract. The indications of a possible pion condensation at the LHC are summarized. The condensation is predicted by the non-equilibrium hadronization model for 2.76 TeV Pb+Pb collisions at the LHC. The model solves the proton/pion puzzle and reproduces the low p T enhancement of the pion spectra, as well as the spectra of protons and antiprotons, charged kaons, K 0 S , K * (892) 0 and φ(1020). The obtained parameters allow to estimate the amount of pion condensate on the level of 5% from the total number of pions at the LHC.

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Cancellation of theσmeson in thermal models

Cited by 74 publications

References 44 publications

Strangeness fluctuations fromK−πinteractions

Strangeness fluctuations fromK−πinteractions

From controversy to precision on the sigma meson: A review on the status of the non-ordinary f0(500) resonance

High temperature Bose-Einstein condensation

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