Commit eafe9c01 authored by Ralf Ulrich's avatar Ralf Ulrich

Merge branch 'master' of gitlab.ikp.kit.edu:AirShowerPhysics/papers/collectivityemhadratio

parents 25be4a18 365a1310
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author = "Pierog, Tanguy and Baur, Sebastian and Dembinski, Hans and Ulrich, Ralf and Werner, Klaus",
title = "{Collective Hadronization and Air Showers: Can LHC Data Solve the Muon Puzzle ?}",
doi = "10.22323/1.358.0387",
journal = "PoS",
year = 2019,
volume = "ICRC2019",
pages = "387"
@article{ Yakutsk,
author = "Glushkov, A.V. and Pravdin, M.I. and Sabourov A.",
title = "",
......@@ -80,15 +80,21 @@ a collective statistical hadronization (core) in addition to the
expected string fragmentation (corona). Since the two mechanisms have
a different electromagnetic energy fraction, we present a possible connection between
statistical hadronization in hadron collisions and muon production in
air showers. Using a novel approach, we demonstrate that the
core-corona effect as observed at the LHC could be part of the solution for
air showers. Using a novel approach, we demonstrate that the upper-limit of
the core-corona effect as observed at the LHC is compatible with a solution of
the lack of muon production in simulations of high energy cosmic rays.
To probe this hypothesis, we study hadronization in high
In order to find an experimental observable to probe this hypothesis in
accelerator experiments, we study hadronization in high
energy hadron collisions using calorimetric information over a large
range of pseudorapidity in combination with the multiplicity of
central tracks. As an experimental observable, we propose the
central tracks. As a result, we propose the
production of energy in electromagnetic particles versus hadrons, as a function of
pseudorapidity and central charged particle multiplicity.
pseudorapidity and central charged particle multiplicity to probe the
core-corona effect in phase space yet unexplored but relevant for air shower
development, in order to have strong constraints for the development of future
hadronic interaction models.
\keywords{LHC, collectivity, core-corona, high energy hadron collisions, EPOS, cosmic ray, extensive air shower, muon production}
......@@ -199,7 +205,19 @@ affects the energy fraction contained in electromagnetic versus hadronic
particles, $R$, and show how this has important possible
implications for the muon production in cosmic ray air showers.
We further propose detailed measurements of $R$ as a novel opportunity to study collective
The goal of this study is not to present a detailed monte-carlo model able
to reproduce all data from accelerator and cosmic experiments, but to
develop a simple able to set a realistic upper-limit of what could be
expected from what is observed at LHC and thus bring enough argument to
justify further experimental studies to constraint future
As a consequence, after showing that this upper-limit is indeed in the
range of the muon deficit observed in the current simulations,
we further
propose detailed measurements of $R$ as a novel opportunity to study collective
hadronization in small systems at the LHC. This may lead to a better
understanding of the underlying nature of statistical hadronization
since different theoretical approaches lead to predictions that
......@@ -408,7 +426,20 @@ starting from zero for low multiplicity $\Pproton{}\Pproton{}$ scattering, up to
more for very high multiplicity $\Pproton{}\Pproton{}$, reaching unity for central
heavy ion collisions (PbPb).
In the following, we are going to employ a straightforward core-corona
In order to know whether such a constrained value of $R$ could be low enough
to increase the number of muons in air shower simulations such that the data
could be reproduced, a simplified core-corona approach can be used to at least
set some realistic upper-limit under the following asumptions :
\item the fraction of core effectively increase with energy: the core-corona approach is originally as a function of the multiplicity and independent of the collision energy for a given multiplicity~\cite{CMS}. Since the average multiplicity increase with the energy, the average core fraction must increase with energy.
\item only the change in hadronization is taken into account: collective effects in core in principle includes particle correlations and flow, but since the longitudinal particle momentum is dominating over the transverse momentum down to relatively low energy, these effects can be neglected in first order.
\item no nuclear effect is introduced: the multiplicity increase with the mass of the projectile, so the core fraction would increase for higher primary mass. To minimize the effect in order to set a conservative upper-limit, this is not taken into account.
\item core-corona effect is applied on full phase space: core hadronization has been observed at mid-rapidity, but in order to see the maximal effect on air shower to set an upper-limit, the modification should apply at larger rapidities.
So in the following, we are going to employ a straightforward core-corona
approach, based on eq.~(\ref{eq:coco}), for any hadronic interaction
model in CONEX air shower simulations. The particle yield from the
chosen interaction model is by definition considered to be the corona
......@@ -603,9 +634,12 @@ showers. There are various indications at the LHC in $\Pproton{}\Pproton{}$ and
collisions that such a scenario is compatible with current
data~\cite{Khachatryan:2010gv,ALICE:2017jyt}, or even suggested by it,
at energy densities as reached by cosmic rays interacting with the
atmosphere~\cite{Anchordoqui:2019laz}. Studying LHC data at mid-rapdity it is found that
atmosphere~\cite{Anchordoqui:2019laz}. Studying LHC data at mid-rapidity it is found that
for events with $\langle{\rm d}N_{\rm ch}/{\rm d}\eta\rangle_{|\eta|<0.5}\sim10$ (corresponding to typical proton-air
interactions) $\fcore$ is already $\approx50$--$75\%$.
At very low energy, where the full phase space is available for measurements, the core fraction is below 5\% which is less than the precision of the models. At RHIC
Since our study is based on the
simple assumption that the full phase space has a modified $\pi^0$
ratio, it remains crucial for cosmic ray physics to conduct further
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