Publications (5)0 Total impact
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ABSTRACT: We present preliminary results on a study about the thermal variation of the
charged and neutral pion masses to one loop, analyzing their electromagnetic
difference, in the context of Chiral Perturbation Theory with two flavours, as
well as using a light resonance model. We find that the pion mass difference
increases for, at least, low and intermediate temperatures, unlike the chiral
limit decreasing result. The axial-vector mixing arising from chiral
restoration smooths the Debye-screening temperature increase. Taking into
account further corrections due to axial and vector resonances, dominated by a1
and rho particles respectively, does not change significantly the ChPT
prediction.
03/2013;
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ABSTRACT: We make a thermal analysis of the light scalar susceptibilities using
SU(3)-Chiral Perturbation Theory to one loop taking into account the QCD source
of isospin breaking (IB), i.e corrections coming from $m_u\neq m_d$. The value
of the connected scalar susceptibility in the infrared regime, the one relevant
when approaching chiral symmetry restoration, and below the critical
temperature is found to be entirely dominated by the $\pi^0-\eta$ mixing, which
leads to model-independent $\mathcal{O}(\epsilon^0)$ corrections, where
$\epsilon\sim m_d-m_u$, in the combination $\chi_{uu}-\chi_{ud}$ of flavour
breaking susceptibilities. We also present preliminary results for the
corrections to the real part of the pion self-energy at nexst-to-leading order
in SU(2)-Chiral Perturbation Theory taking into account electromagnetic
interaction. The zero and finite temperature results for the charged and
neutral pions are given in terms of the three-momentum of the external pion;
and their difference is calculated to this order stressing the fact that, at
low and moderate temperature, the mass splitting $M_{\pi^\pm}-M_{\pi^0}$ grows
with temperature for, at least, non-zero charged pion mass running inside the
loops.
11/2011;
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ABSTRACT: We analyze quark condensates and chiral (scalar) susceptibilities including
isospin breaking effects at finite temperature $T$. These include $m_u\neq m_d$
contributions as well as electromagnetic ($e\neq 0$) corrections, both treated
in a consistent chiral lagrangian framework to leading order in SU(2) and SU(3)
Chiral Perturbation Theory, so that our predictions are model independent. The
chiral restoration temperature extracted from $<\bar q q>= <\bar u u + \bar d d
>$ is almost unaffected, while the isospin breaking order parameter $<\bar u u
- \bar d d >$ grows with $T$ for the three-flavour case SU(3). We derive a sum
rule relating the condensate ratio $<\bar q q>(e\neq 0)/<\bar q q>(e=0)$ with
the scalar susceptibility difference $\chi(T)-\chi(0)$, directly measurable on
the lattice. This sum rule is useful also for estimating condensate errors in
staggered lattice analysis. Keeping $m_u\neq m_d$ allows to obtain the
connected and disconnected contributions to the susceptibility, even in the
isospin limit, whose temperature, mass and isospin breaking dependence we
analyze in detail. The disconnected part grows linearly, diverging in the
chiral (infrared) limit as $T/M_\pi$, while the connected part shows a
quadratic behaviour, infrared regular as $T^2/M_\eta^2$ and coming from
$\pi^0\eta$ mixing terms. This smooth connected behaviour suggests that isospin
breaking correlations are weaker than critical chiral ones near the transition
temperature. We explore some consequences in connection with lattice data and
their scaling properties, for which our present analysis for physical masses,
i.e. beyond the chiral limit, provides a useful model-independent description
for low and moderate temperatures.
01/2011;
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ABSTRACT: We have performed a thermal analysis of the light scalar susceptibilities in
the context of SU(3)-Chiral Perturbation Theory to one loop taking into account
the QCD source of isospin breaking (IB), i.e corrections coming from $m_u\neq
m_d$. We find that the value of the connected scalar susceptibility in the
infrared regime and below the critical temperature is entirely dominated by the
$\pi^0-\eta$ mixing, which leads to model-independent $\mathcal{O}(\epsilon^0)$
corrections, where $\epsilon\sim m_d-m_u$, in the combination
$\chi_{uu}-\chi_{ud}$ of flavour breaking susceptibilities.
01/2011;
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ABSTRACT: We analyze the isospin-breaking corrections to quark condensates within
one-loop SU(2) and SU(3) Chiral Perturbation Theory including $m_u\neq m_d$ as
well as electromagnetic (EM) contributions. The explicit expressions are given
and several phenomenological aspects are studied. We analyze the sensitivity of
recent condensate determinations to the EM low-energy constants (LEC). If the
explicit chiral symmetry breaking induced by EM terms generates a
ferromagnetic-like response of the vacuum, as in the case of quark masses, the
increasing of the order parameter implies constraints for the EM LEC, which we
check with different estimates in the literature. In addition, we extend the
sum rule relating quark condensate ratios in SU(3) to include EM corrections,
which are of the same order as the $m_u\neq m_d$ ones, and we use that sum rule
to estimate the vacuum asymmetry within ChPT. We also discuss the matching
conditions between the SU(2) and SU(3) LEC involved in the condensates, when
both isospin-breaking sources are taken into account.
09/2010;
Institutions
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2011
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Universidad Complutense de Madrid
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Departamento de Física Teórica I
Madrid,
Madrid,
Spain
