simulating pareactions to study the phi meson in nuclear ... · simulating pareactions to study the...
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Simulating pA reactions to study the phi meson in nuclear matter at J-PARC
Talk at the 1st CENuM Workshop for Hadronic Physics
Inha University, Incheon, South Korea
June 18, 2019
Philipp GublerJapan Atomic Energy Agency (JAEA)
Work done in collaboration with
Elena Bratkovskaya (Frankfurt U./GSI)
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φ meson
mφ = 1019 MeVΓφ = 4.3 MeV
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based on hadronic models
PN
P N
Forward KN (or KN) scattering amplitude
P. Gubler and W. Weise, Phys. Lett. B 751, 396 (2015).P. Gubler and W. Weise, Nucl. Phys. A 954, 125 (2016).
Recent theoretical works about the φ
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Recent theoretical works about the φ
D. Cabrera, A.N. Hiller Blin and M.J. Vicente Vacas, Phys. Rev. C 95, 015201 (2017).
based on hadronic models
large dependence on details of the model incorporating Baryon - Vector meson interaction
Spin-Flavor Symmetry extension of standard flavor SU(3)
Hidden Local Symmetry
SU(6):
HLS:
Common features:
strong broadening, small negative mass shift
D. Cabrera, A.N. Hiller Blin and M.J. Vicente Vacas, Phys. Rev. C 96, 034618 (2017).
See also:
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φ meson mass at finite density from QCD sum rules
P. Gubler and K. Ohtani, Phys. Rev. D 90, 094002 (2014).
Most important parameter, that determines the behavior of the φ meson mass at finite density:
Strangeness content of the nucleon
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Vector mesons in experiment
p
e
e
f
E325 (KEK)E16 (J-PARC)
One method: proton induced interactions on nuclei
low (zero?) temperature
no strong interaction
no distortion of signal due to interaction with nuclear medium
approximate density: normal nuclear density ρ0
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7
However, some caution is needed
p e
e
f
Non-trivial non-equilibrium process??
density much below ρ0
large probability of vector meson decay outside of the nucleus
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Experimental di-lepton spectrum
pe
ef
outside decay
pe
e
f
inside decay
Experimentally observed spectrum+ =
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R. Muto et al. (E325 Collaboration), Phys. Rev. Lett. 98, 042501 (2007).
Experimental results (E325, KEK)
Pole mass:
Pole width:
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How compare theory with experiment?
Theory
p e
e
f
Experiment
Realistic simulation of pA reaction is needed!
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Our tool: a transport codePHSD (Parton Hadron String Dynamics)
W. Cassing and E. Bratkovskaya, Phys. Rev. C 78, 034919 (2008).W. Cassing and E. Bratkovskaya, Phys. Rept. 308, 65 (1999).W. Cassing, V. Metag, U. Mosel and K. Niita, Phys. Rept. 188, 363 (1990).
The Vlasov-Uehling-Uhlenbeck type equation for each particle type
Starting point:
mean field(tuned to reproduce nuclear matter properties)
particle distribution function
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„Testparticle“ approachBasic Ingredient:
PHSD (Parton Hadron String Dynamics)
The classical equation of motion are solved for each particle separately
If particles collide with large enough energy
New particles are produced according to experimental cross-sections or models
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Example of a PHSD calculationAu+Au collision at s1/2 = 200 GeV, b = 2 fm
nucleonsquarksgluons
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Advantage: vector meson spectra can be chosen freely
Our first choice: a Breit-Wigner with density dependent mass and width
with
and(corresponds to the result found
in the E325 experiment)
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A first look at a reaction to be probed at J-PARC:
pA reaction with 30 GeV protons A: Copper
A first look at the reaction:Rapidity distribution of protons/mesons
Due to the large collision energy, the incoming
proton passes through the target nucleus
Average of 400 simulated reactions
pA collisions with initial proton energy of 30 GeV
nucleon target after collision
projectile proton after collision
Prel
imin
ary
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What happens with the ϕ?
p+Cu at 12 GeV
Production
p+Cu at 12 GeV
Decay
p+Cu at 12 GeV
p+Cu at 12 GeV
Almost all ϕ mesons are created at early collision time and at large density
Only ϕ mesons which decay early, decay in a dense environment
All preliminary
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The dilepton spectrum
p+Cu at 12 GeV
The ϕ meson peak is clearly visible.
Preliminary
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The dilepton spectrum in the ϕ meson region
p+Cu at 12 GeV
no acceptance corrections
no finite resolution effects
Preliminary
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Divided into different βγ regionsslow middle fast
All preliminary
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Taking into account acceptance correctionsslow middle fast
All preliminary
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The dilepton spectrum in the ϕ meson region
p+Cu at 12 GeV
Preliminary
with acceptance corrections
with finite resolution effects
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Divided into different βγ regions (with acceptance corrections) (with finite resolution) All preliminary
slow middle fast
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To be done
Determine which spectral function best reproduces the E325 experimental data (might not be unique)
Make predictions for the E16 experiment at J-PARC
Accumulate more statistics
Incorporate non-trivial (Lorentz violating) momentum dependence of the spectral function into the simulation
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Summary and Conclusions
Numerical simulations of the pA reactions to measured at the E325 experiment at KEK, using the PHSD transport code, are in progress.
To experimentally the modification of the ϕ meson spectral function at finite density is non-trivial. A good understanding of the underlying pA reaction is needed!
Results will provide important insights for the future E16 experiment at J-PARC
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Backup slides
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Recent theoretical works about the φbased on the quark-meson coupling model
J.J. Cobos-Martinez, K. Tsushima, G. Krein and A.W. Thomas, Phys. Lett. B 771, 113 (2017).J.J. Cobos-Martinez, K. Tsushima, G. Krein and A.W. Thomas, Phys. Rev. C 96, 035201 (2017).
Some φA bound states might exist, but they have a large width
→ difficult to observe experimentally ?
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Our tool: a transport codePHSD (Parton Hadron String Dynamics)W. Cassing and E. Bratkovskaya, Phys. Rev. C 78, 034919 (2008).W. Cassing and E. Bratkovskaya, Phys. Rept. 308, 65 (1999).W. Cassing, V. Metag, U. Mosel and K. Niita, Phys. Rept. 188, 363 (1990).
Solve a Vlasov-Uehling-Uhlenbeck type equation for each particle type
Basic Ingredient 1:
mean field(tuned to reproduce nuclear matter properties)
particle distribution function
„Testparticle“ approachBasic Ingredient 2:
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QCD sum rulesMakes use of the analytic properties of the correlation function:
is calculated “perturbatively”,
using OPEspectral function of the operator χ
After the Borel transformation:
M.A. Shifman, A.I. Vainshtein and V.I. Zakharov, Nucl. Phys. B147, 385 (1979); B147, 448 (1979).
q2
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perturbative Wilson coefficientsnon-perturbative condensates
More on the operator product expansion (OPE)
Change in hot or dense matter!
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Structure of QCD sum rules for the phi meson
Dim. 0:
Dim. 2:
Dim. 4:
Dim. 6:
In Vacuum
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In Nuclear Matter
Structure of QCD sum rules for the phi meson
Dim. 0:
Dim. 2:
Dim. 4:
Dim. 6:
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The strangeness content of the nucleon: results from lattice QCD
Two methodsDirect measurement
A. Abdel-Rehim et al. (ETM Collaboration), Phys. Rev. Lett. 116, 252001 (2016).
Feynman-Hellmann theorem
S. Durr et al. (BMW Collaboration), Phys. Rev. Lett. 116, 172001 (2016).
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Recent results from lattice QCD
P. Gubler and D. Satow, arXiv:1812:00385 [hep-ph], to be published in Prog. Part. Nucl. Phys.
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Compare Theory with Experiment
Experiment
Sum Rules + Experiment
Lattice QCD
Not consistent?
Will soon be measured again with better statistics at the E16 experiment at J-PARC!
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Other experimental resultsThere are some more experimental results on the φ-meson width in nuclear matter,
based on the measurement of the transparency ratio T:
T. Ishikawa et al, Phys. Lett. B 608, 215 (2005).
Measured at SPring-8 (LEPS)
A. Polyanskiy et al, Phys. Lett. B 695, 74 (2011).
Measured at COSY-ANKE
Theoretical calculation:V.K. Magas, L. Roca and E. Oset, Phys. Rev. C 71, 065202 (2005).
Theoretical calculation:E. Ya. Paryev, J. Phys. G 36, 015103 (2009).
Theoretical calculation:D. Cabrera, L. Roca, E. Oset , H. Toki and M.J. Vicente Vacas, Nucl. Phys. A733, 130 (2004).
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Starting point
Rewrite using hadronic degrees of freedom
Kaon loops
(vector dominance model)
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Vacuum spectrum
Data fromJ.P. Lees et al. (BABAR Collaboration), Phys. Rev. D 88, 032013 (2013).
(Vacuum)
How is this spectrum modified in nuclear matter?
Is the (modified) spectral function consistent with QCD sum rules?
P. Gubler and W. Weise, Phys. Lett. B 751, 396 (2015).
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More on the free KN and KN scattering amplitudes
For KN: Approximate by a real constant (↔ repulsion)
T. Waas, N. Kaiser and W. Weise, Phys. Lett. B 379, 34 (1996).
For KN: Use the latest fit based on SU(3) chiral effective field theory, coupled channels and recent experimental results (↔ attraction)
Y. Ikeda, T. Hyodo and W. Weise, Nucl. Phys. A 881, 98 (2012).
K-p scattering length obtained from kaonic hydrogen (SIDDHARTA Collaboration)
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The strangeness content of the nucleon: Important parameter for dark-matter searches:
Adapted from: W. Freeman and D. Toussaint (MILC Collaboration), Phys. Rev. D 88, 054503 (2013).
most important contribution
dominates
Neutralino: Linear superposition of the Super-partners of the Higgs, the photon and the Z-boson
A. Bottino, F. Donato, N. Fornengo and S. Scopel, Asropart. Phys. 18, 205 (2002).
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In-nucleus decay fractions for E325 kinematics
Taken from: R.S. Hayano and T. Hatsuda, Rev. Mod. Phys. 82, 2949 (2010).