A generalized approach to study low as well as high pT regime of transverse momentum spectra
Rohit Gupta
Department of Physical Sciences Indian Institute of Science Education and Research, Mohali
July 30, 2020
1_Rohit_Gupta 1
Rohit Gupta (IISER Mohali) ICHEP 2020 Introduction
Transverse momentum (pT ) spectra is an important observable to understand the evolution dynamics of QCD matter produced during heavy ion collision.
Asymptotic freedom constrain us from applying perturbative QCD theories to study the pT spectra in low pT region. Hence we rely on the phenomenological models with most common being statistical thermodynamics based models.
1_Rohit_Gupta 2
Rohit Gupta (IISER Mohali) ICHEP 2020 Conventional Approach
Considering the fireball produced in HIC as a thermal system, natural choice is that it will follow Boltzmann-Gibbs (BG) statistics.
104 3 2 3 Boltzmann Fit to PbPb data + d N 1 d N gVmT −mT 10 π at 2.76 TeV
E = = exp •2 3 3 102 dp 2πpT dpT dy (2π) kT 10 (GeV/c) dy T N 2 1 d dp T p − N 1 1 10 π 2 Since BG statistics does not explains the data 10−2
− 10 3 well, so we move to a more generalized 0.5 1 1.5 2 2.5 3 p (GeV/c) distribution. Tsallis statistics is a generalised T BG statistics which also takes into account 104 Tsallis Fit to PbPb data at 2.76 TeV non-extensivity in the system. 103 •2 π+ 0 to 5% 102 (GeV/c)
Tsallis fit deviates from data towards higher dy 10 T N 2 d dp T p 1 N 1 pT corresponding to particle from hard π 2 10−1 processes. 10−2 0.5 1 1.5 2 2.5 3 3 2 −q p (GeV/c) d N 1 d N gVm h m i T E = = T 1 + (q − 1) T q−1 3 3 dp 2πpT dpT dy (2π) T 1_Rohit_Gupta 3
Rohit Gupta (IISER Mohali) ICHEP 2020 Pearson Distribution
We have constructed a unified model to explain both soft as well hard part of transverse momentum spectra. It is a generalised form of many probability distribution functions like gaussian, exponential, gamma distributions etc.
105 1 dp(x) a + x 0 to 5% × 2 + = 0 10 to 20% 2 p(x) dx b0 + b1x + b2x •2 103 30 to 40% 50 to 60% f h p(x) = C(e + x) (g + x) (GeV/c)
dy 10 T N 2 d dp
q T p −n p − p t t q−1 N 1
π −1 f (pT ) = B 1 + 1 + (q − 1) 2 10 p0 T
− 10 3 1 2 3 4 5 p (GeV/c) We also observed the indication of T initial geometric effects in the Pearson parameter. 1_Rohit_Gupta 4 Reference: S. Jena and R. Gupta, Phys. Lett. B807, 135551 (2020) Rohit Gupta (IISER Mohali) ICHEP 2020 40th International Conference on High Energy Physics Prague, 2020
Twisted particles in heavy- ion collisions Alexander J. Silenko++ק, Pengming Zhang●, Liping Zou+
§ presenter + Institute for Nuclear Research, Dubna, Russia + Institute of Modern Physics CAS, Lanzhou, China ×Research Institute for Nuclear Problems, BSU, Minsk, Belarus
● School of Phys. & Astron., Sun Yat-sen Univ., Zhuhai, China
28 July – 6 August 2020 2_Alexander_Silenko 5
Twisted (vortex) particles
Twisted (vortex) particles possess an intrinsic orbital angular momentum (OAM) and can be presented by wave beams and packets. Wave beams/packets are localized with respect to two/three dimensions and are described by two/three discrete transverse quantum numbers. Free twisted particle beams of photons, electrons, and neutrons are Laguerre-Gauss beams and can be described by the wave function
2_Alexander_Silenkowhere η is the spin function and the amplitude A and the phase Φ are real. 2 6 Vorticity and hydrodynamic helicity in heavy-ion collisions An analysis of experimental data unambiguously shows that the strongly interacting nuclear fluid appeared as a result of heavy-ion collisions is vortex and can be characterized by the vorticity field. Specific toroidal structures of vorticity field (femtometer vortex sheets) are formed.
The vortex sheet Quadrupole structure of longitudinal vorticity In particular, this effect leads to a significant polarization of Λ-hyperons produced in heavy-ion collisions. M. Baznat, K. Gudima, A. Sorin, O. Teryaev, Phys. Rev. C 88, 061901(R) (2013); 93, 031902(R) (2016); 97, 041902(R) (2018); O. Teryaev, R. Usubov, Phys. Rev. C 92, 014906 (2015); O. V. Teryaev, V. I. Zakharov, Phys. Rev. D 96, 096023 (2017); G.Yu2_Alexander_Silenko. Prokhorov, V.I. Zakharov, O.V. Teryaev, EPJ Web Conf. 191, 05006 (2018).3 7 Importance of production of twisted particles at heavy-ion collisions Is such a production rare? No, it isn’t. M. Katoh et al., Phys. Rev. Lett. 118, 094801 (2017). ``This work indicates that twisted photons are naturally emitted by free electrons and are more ubiquitous in laboratories and in nature than ever thought.’’ (Twisted Radiation from an Electron in Spiral Motion has been studied.) This conclusion has been perfectly confirmed in the following theoretical and experimental papers: T. Kaneyasu et al., J. Synchrotron Rad. 24, 934 (2019); S. V. Abdrashitov et al., Phys. Lett. A 382, 3141 (2018); V. Epp, J. Janz, M. Zotova, Nucl. Instrum. Methods Phys. Res. B 436, 78 (2018); M. Katoh et al., Sci. Rep. 7, 6130 (2017); O. V. Bogdanov, P. O. Kazinski, G. Yu. Lazarenko, Phys. Rev. A 97, 033837 (2018); Phys. Rev. D 99, 116016 (2019); Phys. Lett. A 406, 114 (2019); V. Epp, U. Guselnikova, Phys. Lett. A 383, 2668 (2019). We predict that the production of other (massive) twisted particles with different spins should be ordinary at noncentral heavy-ion collisions due to a fast rotation of the nuclear fluid. We have found the relativistic Hamiltonian 22 10 m p ω L S, 01 and stationary states of a free particle in a uniformly rotating frame 2_Alexander_Silenko 4 8 being Laguerre-Gauss beams with a fixed orbital angular momentum. CANWECONTRAIN ANOMALOUSMAGNETICAND/ORELECTRICDIPOLEMOMENTS OF τ LEPTONFROM PbPb → PbPbτ +τ − REACTION AT THE LHC?
Antoni Szczurek1,2 1 Institute of Nuclear Physics Polish Academy of Sciences, 2University of Rzeszów
M. Dyndal, M. Kłusek-Gawenda, A. Szczurek and M. Schott, Anomalous electromagnetic moments of τ lepton in γγ → τ +τ − reaction in Pb+Pb colli- sions at the LHC, arXiv: 2002.05503. AA → AAτ +τ − framework γγ → τ +τ − process Fiducial selection of τ decays. Results and discussion 3_Antoni_Szczurek THE HENRYK NIEWODNICZAŃSKI9 INSTITUTE OF NUCLEAR PHYSICS POLISH ACADEMY OF SCIENCES
UPC VSANOMALOUSMAGNETICMOMENT A.SZCZUREK KRAKÓW,JULY 28 - AUGUST 6, 2020 1/9 INTRODUCTION
UPC of heavy ions provide a very clean enviroment to study two-photon induced processes Study Pb + Pb → Pb + Pb + τ +τ − at the LHC The presence of γττ vertex (twice) gives sensitivity to anomalous magnetic moment (beyond Standard Model).
The strongest experimental constraints on aτ comes from DELPHI(LEP2) measurement on e+e− → e+e−τ +τ −
-0.052 < aτ < 0.013 The theoretical Standard Model value is significantly smaller than the currently available
th aτ = 0.00117721 ± 0.00000005 BSM: 4 lepton compositness, 4 TeV-scale leptoquarks, 4 left-right symmetric models, 4 unparticle physics
Also electric dipole moment dτ can be studied
3_Antoni_Szczurek THE HENR10YK NIEWODNICZAŃSKI INSTITUTE OF NUCLEAR PHYSICS POLISH ACADEMY OF SCIENCES
UPC VSANOMALOUSMAGNETICMOMENT A.SZCZUREK KRAKÓW,JULY 28 - AUGUST 6, 2020 2/9 THEORETICALFRAMEWORK
The nuclear cross section for the production of l+l− pair in ultraperipheral ultrarelativistic heavy ion collision is calculated in the impact parameter space (Kłusek-Gawenda and Szczurek): Z + − √ + − 2 σ AA → AAl l ; sAA = σ γγ → l l ; Wγγ N(ω1, b1)N(ω2, b2)Sabs(b)
Wγγ 2 × dWγγ dY + − dbx dby d b . (1) 2 l l The amplitude for the γγ → l+l− reaction for the t- and u-channel is:
(γl+l−) µ i(6pt + ml ) (γl+l−) ν M = (−i) u¯(p ) iΓ (p , p ) iΓ (p 0 − p ) 1µ 2ν 3 3 t 2 t 4 t − ml + i
(γl+l−) ν i(6pu + ml ) (γl+l−) µ +iΓ (p , p ) iΓ (p 0 − p ) v(p ) . (2) 3 u 2 u 4 4 u − ml + i Here we introduce photon-lepton vertex function that is a function of momentum transfer.
+ − (γl l ) 0 2 i ν 2 i 5 ν 2 iΓµ (p , p) = −ie γµF1(q ) + σµν q F2(q ) + γ σµν q F3(q ) , (3) 2ml 2ml
i 2 2 2 σµν = [γµ, γν ], F (q ) and F (q ) are the Dirac and Pauli form factors, F (q ) is the electric 2 1 2 3 dipole form factor. The differential cross section for the dilepton production in the γγ-fusion: + − dσ(γγ → l l ) 2π pout 1 X 2 THE HENRYK NIEWODNICZAŃSKI 3_Antoni_Szczurek = |M| . INSTITUTE11 OF NUCLEAR(4) PHYSICS dz 64π2s p 4 POLISH ACADEMY OF SCIENCES in spin UPC VSANOMALOUSMAGNETICMOMENT A.SZCZUREK KRAKÓW,JULY 28 - AUGUST 6, 2020 3/9 ELEMENTARY CROSS SECTION, aτ DEPENDENCE
20 102 a = +0.1 a = +0.1 τ τ ) [nb]
• 18 = 0.0 = 0.0 τ + )/dz [nb] τ
= •0.1 • = •0.1 τ +
→ 16 τ γ γ ( → γ σ 14 γ ( 10 σ 12 d
10
8
6 1
4 4 6 8 10 12 14 −1 −0.5 0 0.5 1 W [GeV] z (a) (b)
FIG.: (a) Elementary cross section as a function of energy (b) Differential cross as a function of z = cos θ for fixed value of energy
3_Antoni_Szczurek THE HENR12YK NIEWODNICZAŃSKI INSTITUTE OF NUCLEAR PHYSICS POLISH ACADEMY OF SCIENCES
UPC VSANOMALOUSMAGNETICMOMENT A.SZCZUREK KRAKÓW,JULY 28 - AUGUST 6, 2020 4/9 NUCLEARCROSSSECTION, aτ DEPENDENCE
6 p • no cut =0) τ
τ t, sNN=5.02 TeV, UPC ; a • p > 1 GeV τ 5 t,τ + τ
PbPb 4 → (PbPb
σ 3 ) / • τ + τ 2 PbPb → 1 (PbPb σ 0 −0.4 −0.2 0 0.2 0.4 aτ
FIG.: Ratio of the total nuclear cross sections for Pb+Pb→Pb+Pbττ production at the LHC energies as a function of aτ , relative to SM (aτ = 0). τ The ratio of the cross sections for extra pT > 1 GeV is also shown. 3_Antoni_Szczurek THE HENR13YK NIEWODNICZAŃSKI INSTITUTE OF NUCLEAR PHYSICS POLISH ACADEMY OF SCIENCES
UPC VSANOMALOUSMAGNETICMOMENT A.SZCZUREK KRAKÓW,JULY 28 - AUGUST 6, 2020 5/9 FIDUCIALSELECTIONAND τ DECAYS
Tau is the heaviest lepton with a lifetime of 3 × 10−13 that can decay into lighter leptons (electron or muon) or hadrons (mainly pions and kaons). The primary τ decay channels produce one charged particle (denoted as 1ch, or one-prong):
τ → ντ + ` + ν` (` = e, µ)
± 0 τ → ντ + π + nπ
or three charged particles (denoted as 3ch, or three-prong):
± ∓ ± 0 τ → ντ + π + π + π + nπ
Approximately 80% of all τ decays are the one-prong decays and 20% of them are the three-prong decays. In order to model τ decays we use Pythia 8.243 program. We propose that the γγ → τ +τ − candidates events are selected by requiring at least one τ lepton to decay leptonically, as this allows that existing triggering algorithms of the ATLAS or CMS detector can be used. The leading electron or muon is required to have pT > 4 GeV and |η| < 2.5.
3_Antoni_Szczurek THE HENR14YK NIEWODNICZAŃSKI INSTITUTE OF NUCLEAR PHYSICS POLISH ACADEMY OF SCIENCES
UPC VSANOMALOUSMAGNETICMOMENT A.SZCZUREK KRAKÓW,JULY 28 - AUGUST 6, 2020 6/9 RESULTS
l 102 l 102 R → ττ R → ττ PbPb PbPb , sNN=5.02 TeV PbPb PbPb , sNN=5.02 TeV τ τ τ τ τ τ τ τ l 1ch + l 3π categories l 1ch + l 3π categories
10 aτ = 0 10 aτ = 0 aτ = -0.1 aτ = +0.1 aτ = -0.05 aτ = +0.05 aτ = -0.02 aτ = +0.02 1 1
10−1 10−1
4 6 8 10 12 14 16 18 20 4 6 8 10 12 14 16 18 20 plead. lepton [GeV] plead. lepton [GeV] (a) T (b) T
+ − + − FIG.: Ratio of the fiducial cross sections between γγ → τ τ and γγ → ` ` (` = e or µ) processes as a function of pT of the leading lepton for all event categories summed together.
3_Antoni_Szczurek THE HENR15YK NIEWODNICZAŃSKI INSTITUTE OF NUCLEAR PHYSICS POLISH ACADEMY OF SCIENCES
UPC VSANOMALOUSMAGNETICMOMENT A.SZCZUREK KRAKÓW,JULY 28 - AUGUST 6, 2020 7/9 RESULTS
7 2 nb-1, 5% sys. OPAL 1998 6 -1 2 nb , 1% sys. L3 1998 5 20 nb-1, 1% sys. DELPHI 2004 4
3 Pb+Pb, 2 nb-1, 5% sys
2 Pb+Pb, 2 nb-1, 1% sys
Expected significance [std. deviation] -1 1 Pb+Pb, 20 nb , 1% sys
0 −0.03 −0.02 −0.01 0 0.01 0.02 0.03 −0.08 −0.06 −0.04 −0.02 0 0.02 0.04 0.06 0.08 (a) aτ 95% CL limit on aτ
FIG.: (a) Expected signal significance for various assumptions on Pb+Pb integrated luminosity and total systematic uncertainty. (b) Expected 95% CL limits on aτ measurement for various assumptions on Pb+Pb integrated luminosity and total systematic uncertainty.
3_Antoni_Szczurek THE HENR16YK NIEWODNICZAŃSKI INSTITUTE OF NUCLEAR PHYSICS POLISH ACADEMY OF SCIENCES
UPC VSANOMALOUSMAGNETICMOMENT A.SZCZUREK KRAKÓW,JULY 28 - AUGUST 6, 2020 8/9 CONCLUSION
We have used UPC calculation for Pb + Pb → Pb + Pb + τ +τ − + − We have studied the dependence of the γγ → τ τ on aτ All channels with at least one leading lepton have been accepted We suggest to measure the ratio of: γγ → τ +τ − → (...... ) to γγ → e+e−(µ+µ−) The limitations with present data seems better than those from DELPHI Spin-spin correlations probably small
3_Antoni_Szczurek THE HENR17YK NIEWODNICZAŃSKI INSTITUTE OF NUCLEAR PHYSICS POLISH ACADEMY OF SCIENCES
UPC VSANOMALOUSMAGNETICMOMENT A.SZCZUREK KRAKÓW,JULY 28 - AUGUST 6, 2020 9/9 Jan Vanek for the STAR Collaboration Nuclear Physics Institute, Czech Academy of Sciences Faculty of Nuclear Sciences and Physical Engineering, CTU in Prague ICHEP 2020 30. 07. 2020
4_Jan_Vanek 18 D0 (STAR): Phys. Rev. C 99, 034908, (2019). D (ALICE): JHEP 03, 081, (2016).
LBT (S. Cao et al.): Phys. Rev. C 94, 014909, (2016). Duke (Y. Xu et al.): Phys. Rev. C 97, 014907, (2018).
HFT resolution (STAR): : Phys. Rev. Lett. 118, 212301, (2017) ▪ At RHIC energies, charm quarks are produced predominantly through hard partonic scatterings at early stages of Au+Au collisions, making them an excellent probe of the QGP
0 ▪ Suppression of high-pT D is observed in central Au+Au collisions and is comparable to models incorporating both radiative and collisional energy losses, and collective flow
AA d푁D Τd푝T 푅AA 푝T = pp 푁coll d푁D Τd푝T
▪ The Heavy Flavor Tracker allows direct topological reconstruction of three body decay D±→K∓π±π± at mid-rapidity ▪ BR = (8.98 ± 0.28)%, cτ = (311.8 ± 2.1) μm
▪ The study of D± production is complementary to that of D0 and also provides constraints on the total charm cross-section in heavy-ion collisions Jan Vanek, ICHEP 2020 30. 07. 2020 2 4_Jan_Vanek 19 ▪ Invariant spectrum of D± measured in three centrality classes of Au+Au collisions ▪ For all centralities, see my poster (ID: 414)
▪ Nuclear modification factor: Similar level of suppression and centrality dependence for D± and D0
▪ The D±/D0 yield ratio shows good agreement with PYTHIA 8 calculation
p+p reference (STAR): Phys. Rev. D 86, 072013, (2012) Jan Vanek, ICHEP 2020 D0 (STAR): Phys. Rev. C 99, 034908, (2019). 30. 07. 2020 3 4_Jan_Vanek 20 ▪ STAR has extensively studied production of open-charm mesons in Au+Au collisions at sNN=200 GeV utilizing the HFT
▪ The HFT allows direct topological reconstruction of hadronic decays of open-charm mesons
▪ D± invariant spectrum measured for three centrality classes of Au+Au collisions ▪ 0-10%, 10-40%, 40-80%
▪ D± nuclear modification factor is consistent with that of D0 0 ± ▪ D and D mesons are significantly suppressed at high-pT in central Au+Au collisions ▪ Charm quarks interact strongly with the QGP
▪ D±/D0 yield ratio ▪ Agrees with PYTHIA 8 calculation
Acknowledgement: This research is funded by the project LTT18002 of the Ministry of Education, Youth, and Sport of the Czech Republic and from European Regional Development Fund-Project "Center of Advanced Applied Science" No. CZ.02.1.01/0.0/0.0/16-019/0000778
Jan Vanek, ICHEP 2020 30. 07. 2020 4 4_Jan_Vanek 21 Deuteron (and cluster) production
Radka Sochorov´a
ICHEP 2020
30 July 2020
5_Radka_Sochorova 22
Radka Sochorov´a Deuteron (and cluster) production 30 July 2020 , 1 / 4 Clusters and statistical model
Universal description with the statistical model Thermal model vs. Coalescence model Binding energy of deuterons is around 2.2 MeV Both models predict similar deuteron yields Elliptic flow could show differences [A. Andronic et al., J. Phys: Conf. Ser 779 (2017) 012012] between models
Clusters actually carry femtoscopic information about the freeze-out −→ motivation5_Radka_Sochorova for studying clusters 23
Radka Sochorov´a Deuteron (and cluster) production 30 July 2020 , 2 / 4 DRAGON with coalescence
protons and neutrons generated by Monte Carlo generator according to the blast-wave model with resonances
each p-n pair −→ momentum and position of p and n boosted to the 2-particle rest-frame
particle that decoupled earlier −→ propagated to the decoupling time of the other particle
deuteron candidate given by the conditions of ∆p ≤ 0.200 GeV/c and ∆r ≤ 2.1 fm
spin-isospin factor 3/8
5_Radka_Sochorova 24
Radka Sochorov´a Deuteron (and cluster) production 30 July 2020 , 3 / 4 DRAGON with coalescence - deuterons
0.01 0.18 ρ ρ a2 = 0.15, 2 = 0.045, 0 = 1.3, T = 100 MeV ] ALICE data − 30−40% centrality, sqrt(sNN)=2.76 TeV −2 0.16 ρ ρ a2 = 0.03, 2 = 0.012, 0 = 1.4, T = 80 MeV ALICE data − 0−5% centrality, sqrt(s )=2.76 TeV 0.14 NN 0.12
dy [(GeV/c) 0.1 ) T T dp
0.001 (p 0.08 T 2 v
) p 0.06 π
(2 0.04 ev ρ ρ a2=0.15, 2=0.045, 0= 1.3, T=100 MeV 0.02 ALICE data − 20−40%, sqrt(sNN)=2.76 TeV N / ρ ρ 2 a2=0.03, 2=0.012, 0= 1.4, T=80 MeV 0 d ALICE data − 0−5%, sqrt(sNN)=2.76 TeV 0.0001 −0.02 0 0.5 1 1.5 2 2.5 0 0.5 1 1.5 2
pT [GeV/c] pT [GeV/c]
We added coalescence to Monte Carlo generator DRAGON Our model is able to describe the transverse momentum spectra and elliptic flow of protons and deuterons with the same parameters BUT problems with fitting pions For more information you can read my poster (#666) on the INDICO 5_Radka_Sochorovaweb page 25
Radka Sochorov´a Deuteron (and cluster) production 30 July 2020 , 4 / 4 Proton number fluctuations due to mundane effects
Boris Tom´aˇsik
Univerzita Mateja Bela, Bansk´aBystrica, Slovakia and FNSPE, Cesk´evysok´euˇcen´ıtechnick´e,Praha,ˇ Czech Republic [email protected]
collaboration: Ivan Melo
ICHEP 2020 poster #712 poster session Heavy Ions
30.7.2020 6_Boris_Tomasik 26
Boris Tom´aˇsik (Univerzita Mateja Bela) Net proton number fluctuations 30.7.2020 1/4 A quick overview: net-proton number fluctuations
B baryon number susceptibilities χi may indicate critical point they can be measured as cumulants of the net-proton number distribution non-critical effects influencing fluctuations only protons measurable baryon number conservation limited acceptance and efficiency In this work: baryon number conservation protons (seen), neutrons (not seen), and their antiparticles limited acceptance rapidity distribution of wounded nucleons and produced NN¯ pairs We look at the dependence of cumulants on: width of the acceptance rapidity window at midrapidity position of the acceptance window in rapidity collision energy 6_Boris_Tomasikcentrality 27 Boris Tom´aˇsik (Univerzita Mateja Bela) Net proton number fluctuations 30.7.2020 2/4 Rapidity distributions of wounded and produced nucleons
Wounded nucleons Produced NN¯ pairs
Number determined by MC Glauber Mean number ∝ Nw Tuned to data on p − p¯ Tuned to data on number ofp ¯ 90 8 exp. exp. 80 7 70 6 60
/dy 5
/dy 50 w 40 4 BBbar dN 3
30 dN 20 2 10 1 0 0 -4 -2 0 2 4 -4 -2 0 2 4 y y
Illustration for: ym = 1, dy = 0.8 Illustration for: ym = 1, a = 0.08
Parameters6_Boris_Tomasik tuned for each of the RHIC BES energies. 28
Boris Tom´aˇsik (Univerzita Mateja Bela) Net proton number fluctuations 30.7.2020 3/4 Some results
Rapidity dependence of skewness and kurtosis
1 1
0.8 0.8
0.6 0.6 2 σ S
κσ 0.4 0.4 0.2 0.2 7.7 19.6 0 200 0 -0.2 0 0.5 1 1.5 2 0 0.5 1 1.5 2 y y
Collision energy dependence of skewness and kurtosis
1 1 0.9 0.9 0.8 0.8 0.7 0.7
0.6 2 σ 0.6 S 0.5 κσ 0.4 0.5 0.3 0.4 Glauber MC 0.3 0.2 fixed N 0.1 w 0.2 10 100 10 100 1/2 1/2 (sNN) (sNN) 6_Boris_Tomasik 29 B. Tom´aˇsik,I. Melo, L. Laff´ers,M. Bleicher, PoS CORFU2018 (2019) 155 Boris Tom´aˇsik (Univerzita Mateja Bela) Net proton number fluctuations 30.7.2020 4/4 Monte Carlo Simulations of Upsilon Meson Production
Jaroslav Bielcik Jakub Ceska Leszek Kosarzewski Miroslav Myska
Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University (CZ)
Interantional Conference on High Energy Physics Prague 7_Jakub_Ceska 30.7.2020 30
J. Ceska (FNSPE CTU (CZ)) Upsilon production study 30.7.2020 1/3 Motivation
Production mechanism: 〉 7 pp s = 2.76 TeV (1S) ϒ ¯ 〈 pPb s = 5.02 TeV hard scattering - bb production 6 NN
(1S)/ PbPb s = 2.76 TeV ϒ |y NN| < 2.4 bound state formation - colour singlet, 5 CM
colour octet channels 4 ϒ(1S) 〈ϒ(1S)〉 Sensitive to: 3 interplay of soft and hard processes 2 CMS 1 |y | < 1.93 multiple parton interaction CM 0 0 0.5 1 1.5 2 2.5 3 3.5 4 |η|<2.4 |η|<2.4 parton saturation signatures N /〈N 〉 tracks tracks total
> 25 > 25 > 25 Study of: ψ STAR J/ψ ψ PYTHIA8 J/ψ ψ 0
J/ J/ J/ EPOS3.2 D p > 0 GeV/c p > 0 GeV/c 2 < p < 4 GeV/c /
J. Ceska (FNSPE CTU (CZ)) Upsilon production study 30.7.2020 1/3 Results: Upsilon vs Nch/hNchi
Both PYTHIA and Herwig with k⊥ = 20 GeV/c describe a stronger than linear increase in in normalised Upsilon yield dependence on normalised charged particle multiplicity.
Herwig with k⊥ = 4 GeV/c predicts a closer to linear development in higher multiplicities. STAR preliminary data taken from: [L. Kosarzewski [STAR]: Overview of quarkonium production studies in the STAR experiment, Presented7_Jakub_Ceska at FAIRness 2019] 32
J. Ceska (FNSPE CTU (CZ)) Upsilon production study 30.7.2020 2/3 Conclusion
The minimum bias spectra differ significantly for PYTHIA and Herwig in larger multiplicities Upsilon production in Herwig has limited validity
Both PYTHIA and Herwig (k⊥ = 20 GeV/c) predict stronger than linear increase in normalised Upsilon yield in dependence on normalised multiplicity
In comparison to STAR preliminary data both PYTHIA and Herwig (k⊥ = 20 GeV/c) predict higher values for larger multiplicities, while underestimating smaller multiplicity values The data suggests, that Upsilon mesons are produced in multi-parton collisions, due
to stronger than linear increase predicted by PYTHIA and Herwig (k⊥ = 20 GeV/c)
7_Jakub_Ceska 33
J. Ceska (FNSPE CTU (CZ)) Upsilon production study 30.7.2020 3/3