production of strange particles at rhic via quark recombination
DESCRIPTION
Production of strange particles at RHIC via quark recombination. C.B. Yang Institute of Particle Physics, Wuhan, China Collaborated with Rudolph C. Hwa University of Oregon. Outline. Motivations Recombination model Kaon production production Production of and - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/1.jpg)
Production of strange particles at RHIC
via quark recombination C.B. Yang
Institute of Particle Physics, Wuhan, China
Collaborated with
Rudolph C. Hwa
University of Oregon
![Page 2: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/2.jpg)
Outline
MotivationsRecombination modelKaon production productionProduction of and Summary and discussion
![Page 3: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/3.jpg)
1. Motivations• Why we study strange particle production
Most strange particles are produced in the interactions
Relevant to the deconfinement and flavor equilibrium
Dependence on the colliding systemsDependence on the cms energyPossible signal for QGP formationGood test for production mechanism
![Page 4: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/4.jpg)
2. Recombination model• Hadrons are formed by combining quarks• No gluon contribution is considered• This model is successful in explaining non-
strange particle production at RHIC in central and forward directions
• Fragmentation is interpreted as a quark recombination process
• Recombination of soft partons is more effective for producing hadrons with intermediate momentum
![Page 5: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/5.jpg)
Parton distribution (log scale)
(recombine) (fragment)
p
p1+p2p q
meson momentum
higher yield heavy penalty
Why Recombination?
![Page 6: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/6.jpg)
Different implementations
• Duke group etc: 6-dimensional phase spaceusing Wigner function and density matrix
• Oregon group:one-dimensional momentum spaceusing phenomenological recombination function
![Page 7: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/7.jpg)
, ,..., ,...3 31 2 1 2
1 2 31 2 3
( , , ) ( , , )p
pdx xdx dx x xdNx F x x x R
dx x x x x x x
Basic formulas
F: joint parton distributionsR: recombination functions
![Page 8: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/8.jpg)
Ingredients• Soft partons are assumed having exponen
tial pT distributions• Hard parton spectra are calculated from p
QCD, considering shadowing effect etc• Shower parton distributions are known fro
m fitting fragmentation data• Recombination functions are known from f
ormer studies• Energy loss effect can be taken into accou
nt phenomenologically
![Page 9: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/9.jpg)
3. Kaon Production
• Soft partons: known for light quarks; assumed to be exponential in pT for strange quarks with two parameters
• Semihard shower parton distributions known already
• Recombination function for Kaon determined
• Fix the density of strange quarks in the medium by fitting the low pT spectrum
![Page 10: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/10.jpg)
1 2 1 2 1 2
1 1 2 2
1 2 1 2 1 2
( , , ) ( , )
/ , /
1( , ) ( 1)
( 1, 1)
M M M
a bM
R p p p g y y G y y
y p p y p p
G y y y y y yB a b
0
1 1 1 11
2 2
{ }
( ) exp( / )
( ) ( ) ( / )
s s d s sd s
thq
i iik
F TT T S TS SS
dNT p p Cp p T
dp
S p dkkf k S p k
1, (3 1) / 2 2, 1Kg
![Page 11: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/11.jpg)
0
1 1 1 11
2 2
( ) exp( / )
( ) ( ) ( / )
ths
s s s
ss i ii
k
dNT p p C p p T
dp
S p dkkf k S p k
C=23.2 GeV-1, T=0.317GeV
Cs , Ts and ξdetermined from fitting Kaon spectrum
![Page 12: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/12.jpg)
Kaon spectrum
Cs=15.5 GeV-1, Ts=0.323 GeV
![Page 13: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/13.jpg)
4. ΛProduction
• Leading parton contribution to Λspectrum?
• Recombination function is assumed as
1 2 3 1 2 3 1 2 3
1 2 3 1 2 3 1 2 3
( , , , ) ( , , )
/
1( , , ) ( ) ( 1)
( 1, 2) ( 1, 1)
i i
R p p p p g y y y G y y y
y p p
G y y y y y y y y yB B
•Statistical factor for Λ is ¼
• 1, (3 1) / 2 2
![Page 14: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/14.jpg)
ΛSpectrum
No leading partoncontribution
With leading partoncontribution
![Page 15: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/15.jpg)
Λ/K ratio
![Page 16: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/16.jpg)
5. Production of and
They are a measure of the initial state– no rescattering with other hadrons– sensitive to the initial state
Their masses are almost the sum of that of constituent quarks
weak interactions among quarksloosely bound states
![Page 17: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/17.jpg)
Assume valon distributions are
1 2 1 2
1 2 3 1 2 3
( , ) ( 1/ 2) ( 1/ 2)
( , , ) ( 1/ 3) ( 1/ 3) ( 1/ 3)
G y y y y
G y y y y y y
Strange parton distributions are thesame as for other hadrons
![Page 18: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/18.jpg)
Φ spectrum
![Page 19: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/19.jpg)
Ω spectrum
0.3, 0.008g g
![Page 20: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/20.jpg)
Ω/Φ ratio
![Page 21: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/21.jpg)
6.Summary and discussions
• K, Λ,Φ,Ω spectra can be understood in the framework of the recombination model with only three free parameters
• At low pT<4GeV/c, thermal quark recombination dominates for K and Λ
• Shower parton contribution is important for intermediate pT for K and Λ
![Page 22: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/22.jpg)
6.Summary and discussions
• For Φ and Ω,up to pT=8GeV/c, thermal quark recombination dominates, but the shower contribution is visible in the Ω / Φ ratio
• Competition effect plays an important role in explaining the yields of Φ and Ω
![Page 23: Production of strange particles at RHIC via quark recombination](https://reader030.vdocument.in/reader030/viewer/2022032612/56813237550346895d989d56/html5/thumbnails/23.jpg)