1.
Are there more (stable) s-quarks than anti_s-quarks in the universe?
Answer by H. Stroebele:
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After a discussion during the Thursday afternoon session the answer seems to be that it is very likely but not certain that hyperons or s-quarks "survive" in the interior of neutron stars.
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2.
J. Stroth
Which are the experimental evidences for a long mean free path of phi mesons in medium?
For the answer see file Phi.pdf which is uploaded to the same indico page.
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3.
Question to question-by-Dr.NuXu (at Hades Talk by H.Schuldes).
My question "How much is it essential, to understand low-pt enhancement of pi-/pi+ ratio ?"
I am asking because for example, Dr. CBlume, Dr. CMKo (and other speaker) mentioned that "strangenes exchange through
" π + Λ => K− + N " takes big role for interpretation".
Susumu SATO (J-PARC/JAEA)
Ps: I am asking also because "Hyperon (S=-1, -2, -3) yield normalized by pion yield are used for the increase/decrease arguments".
Answer by H. Stroebele
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The low pt enhancement is -at least partly- due to a Coulomb effect. The slow (low pt) pi^+ are repelled by the positive charge of the proton participants whereas the pi^- are attracted. These actions on the charged pions do not change their multiplicities (after integration over tranverse momentum).
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4.
To: Neutron Star "Equation of State" people
Regarding developing an acceptable 'equation of state' for the neutron star, do we know which theoretical models are being actively pursued by (which) experiments to prove/disprove them?
And which model has been the most successful as of now?
e.g. Is it Walecka model or any other model?
Answer by David Blaschke
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An equation of state (EoS) for neutron star applications usually stems from one of the two classes:
A) "ab-initio", which are based on interaction potentials between nucleons (baryons) in free space as inferred from phase shifts and/or nuclear binding energies, and which use many-particle theories such as (Dirac-)Brueckner-Hartree-Fock (DBHF) or Brueckner-Bethe-Goldstone (BBG) to arrive at the EoS. Here the EoS based on the Bonn-A or Bonn-BC interactions are most successfully applied to describe neutron star properties.
B) (relativistic) density functional approaches of the Skyrme type (like the Walecka model), which use data of finite nuclei or their extrapolations to infinite nuclear matter for fitting their parameters. The most popular representatives are the DD2 model (S. Typel at al., PRC 81 (2010) 015803; arxiv:0908.2344) and the Brussels-Montreal models BSk19 - BSk21 (A. Potekhin et al., A&A 560 (2013) A48; arxiv:1310.0049).
Under "ab-initio" one could count also perturbative approaches using chirally constrained interactions basen on pion-exchange and denoted as chiral effective field theories (ChEFT). Their application, however, is bound to the low-density (subnuclear density) region. Here their results are used as constraints for other approaches.
For supranuclear densities, these EoS have to fulfill a number of constraints from neutron star and heavy-ion collision physics. A representative collection of those constraints is given in T. Klaehn et al., PRC 74 (2006) 035802; nucl-th/0602038; with an update given in T. Klaehn et al., Phys. Part. Nucl. Lett. 9 (2012) 484; arxiv:1101.6061.
Here the constraint on the predicted (minimal) maximum mass of neutron stars (M_max > 2.01 +/- 0.04 M_sun; J. Antoniadis et al. Science 340 (2013) 6131) plays a key role for selecting viable EoS models.
and a hint from Stefan Typel
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to a review with an overview over EOS, models, and constraints:
M. Oertel et al., Rev. Mod. Phys. 89, 015007 (2017)
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5.
Hi,
A Question concerning the opening question of the session. "Is there any net stable strangeness in the universe?"
One place to look for this is the Atlas W+charm result that was interpreted as a strange PDF that is more than just sea quarks. Is there any effort ongoing to put electroweak corrections on the lattice or in PDF calculations? EW corrections will be different for s and sbar in the presence of u u d inside the proton or other quarks in other hadrons.
Answer from Frithjof Karsch:
Yes, this are interesting questions. However, I fear that the lattice at
present can not contribute to this. There are lattice QCD calculations
done that include the electromagnetic force. I do not know of any that
try to incorporate the electro-weak sector.
Of course, lattice QCD calculations are done with different values of
the strangeness chemical potential and the effect of a non-zero strangeness
chemical potential has to some extent been looked at. Effects are not dramatic
but visible in the EoS.
In fact, as the evolution of the early universe is not strongly constraint in the
electro-weak sector also the strangeness chemical potential is not well known
(e-Print: arXiv:0906.3434 [arXiv.org] [hep-ph] )
Looking at this is one project in our Transregio. PIs are Dominik Schwarz in
Bielefeld and Juergen Schaffner-Bielich in Frankfurt. You may want to discuss
also with them?
regards,
Frithjof
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