scholarly journals Dielectrons and Direct Virutal Photons at RHIC-STAR

2020 ◽  
Vol 235 ◽  
pp. 02002
Author(s):  
Chi Yang
Keyword(s):  
Mass Spectrum ◽  
Invariant Mass ◽  
Virtual Photon ◽  
Invariant Mass Spectrum ◽  
Heavy Ion ◽  
Relativistic Heavy Ion Collisions ◽  
Dense Medium ◽  
Model Calculations ◽  
Ion Collisions ◽  
Low Mass

Electromagnetic probes are unique probes of the hot and dense medium cre- ated in relativistic heavy-ion collisions due to their minimal interactions with the partonic and hadronic medium. They can be produced at all stages of a collision, thus they provide unique ways to study the medium properties of the whole collision evolution. We present the dielectron invariant mass spectrum at √sNN = 27, 39, 39, and 62.4 GeV. Comparing to hadronic cocktail simulation, significant excesses of dielectron invariant mass spectrum at low mass are observed. The direct virtual photon invariant yields derived from the low-mass e+e− continuum in Au+Au collisions at √sNN = 200 GeV is presented and the excesses from thermal photons in low transverse momentum (pT) have been observed. Model calculations can simultaneously describe both dielectron low mass excesses and direct virtual photon low pT excesses.

Contribution ofπ0and η Dalitz decays to the dilepton invariant-mass spectrum in1AGeV heavy-ion collisions

1997 ◽  
Vol 56 (6) ◽  
pp. R2920-R2923 ◽  
Author(s):  
R. Holzmann ◽  
M. Appenheimer ◽  
R. Averbeck ◽  
Y. Charbonnier ◽  
H. Delagrange ◽  
...  
Keyword(s):  
Mass Spectrum ◽  
Invariant Mass ◽  
Heavy Ion Collisions ◽  
Invariant Mass Spectrum ◽  
Heavy Ion ◽  
Dilepton Invariant Mass ◽  
Ion Collisions

SEARCH FOR NEUTRAL BOSONS IN RELATIVISTIC HEAVY-ION COLLISIONS

2008 ◽  
Vol 17 (05) ◽  
pp. 759-770 ◽  
Author(s):  
P. L. JAIN
Keyword(s):  
Invariant Mass ◽  
Heavy Ion Collisions ◽  
Life Time ◽  
Heavy Ion ◽  
Relativistic Heavy Ion Collisions ◽  
Electron Pairs ◽  
Ion Collisions ◽  
Low Mass

In this talk, I will describe results on 1,220 electron pairs produced from a 207 Pb beam at 160A GeV in a nuclear experiment EMU 11 conducted at the CERN SPS. These electron pairs were produced at a distance of more than 50 μm from the primary interactions, which eliminates contamination due to Dalitz pairs. Results on electron pairs with invariant mass Q ranging between 1 and 100 MeV and life-time τ between 10−15 s and 10−12 s were analyzed. After subtracting background pairs from the materialization of photons and from the decays of π0 to photons from the data, they exhibit an enhancement at low mass Q = 6 – 20 MeV with narrow peaks at 7 ± 1 MeV , 19 ± 1 MeV and τ ≤ 10−13 s .

Bremsstrahlung production of low mass dielectrons in relativistic heavy ion collisions

1996 ◽  
Vol 54 (3) ◽  
pp. 1366-1374 ◽  
Author(s):  
Dipali Pal ◽  
Kevin Haglin ◽  
Dinesh Kumar Srivastava
Keyword(s):  
Heavy Ion Collisions ◽  
Heavy Ion ◽  
Relativistic Heavy Ion Collisions ◽  
Ion Collisions ◽  
Low Mass

scholarly journals Highlights from PHENIX at RHIC

2018 ◽  
Vol 171 ◽  
pp. 01003
Author(s):  
Rachid Nouicer
Keyword(s):  
Heavy Quark ◽  
Heavy Ion Collisions ◽  
Meson Production ◽  
Heavy Ion ◽  
Relativistic Heavy Ion Collisions ◽  
Dense Medium ◽  
Heavy Flavor ◽  
Theoretical Understanding ◽  
Rapidity Region ◽  
Ion Collisions

Hadrons conveying strange quarks or heavy quarks are essential probes of the hot and dense medium created in relativistic heavy-ion collisions. With hidden strangeness, ϕ meson production and its transport in the nuclear medium have attracted high interest since its discovery. Heavy quark-antiquark pairs, like charmonium and bottomonium mesons, are mainly produced in initial hard scattering processes of partons. While some of the produced pairs form bound quarkonia, the vast majority hadronize into particles carrying open heavy flavor. In this context, the PHENIX collaboration carries out a comprehensive physics program which studies the ϕ meson production, and heavy flavor production in relativistic heavy-ion collisions at RHIC. In recent years, the PHENIX experiment upgraded the detector in installing silicon vertex tracker (VTX) at mid-rapidity region and forward silicon vertex tracker (FVTX) at the forward rapidity region. With these new upgrades, the experiment has collected large data samples, and enhanced the capability of heavy flavor measurements via precision tracking. This paper summarizes the latest PHENIX results concerning ϕ meson, open and closed charm and beauty heavy quark production in relativistic heavy-ion collisions. These results are presented as a function of rapidity, energy and system size, and their interpretation with respect to the current theoretical understanding.

OBSERVATION OF THE ABC EFFECT IN THE FIRST EXCLUSIVE MEASUREMENTS OF pn → dπ0π0

2007 ◽  
Vol 22 (02n03) ◽  
pp. 617-620 ◽  
Author(s):  
◽  
O. Khakimova ◽  
M. Bashkanov ◽  
T. Skorodko ◽  
C. Bargholtz ◽  
...  
Keyword(s):  
Mass Spectrum ◽  
Invariant Mass ◽  
Bound States ◽  
Fundamental System ◽  
Theoretical Models ◽  
Invariant Mass Spectrum ◽  
High Mass ◽  
Threshold Enhancement ◽  
Low Mass ◽  
Mass Enhancement

The reaction pn → dπ0π0 constitutes the most fundamental system for the study of the ABC effect - a puzzling threshold enhancement in the ππ invariant mass spectrum of the ππ system in double-pionic fusion to nuclear bound states. The first exclusive measurements of this reaction have now been carried out at CELSIUS-WASA. They exhibit a striking low-mass enhancement in the ππ invariant mass spectrum, prove it to be a σ-channel phenomenon and falsify conventional theoretical models, which predict an associated high-mass enhancement not present in the new exclusive data. In the kinematically complete data sample we observe a ΔΔ excitation, where the interaction between the two Δ obviously plays a crucial role for the generation of the ππ low-mass enhancement.

scholarly journals Heavy flavour production at RHIC and LHC

2018 ◽  
Vol 171 ◽  
pp. 04001 ◽  
Author(s):  
Gian Michele Innocenti
Keyword(s):  
Energy Loss ◽  
Quark Matter ◽  
Heavy Ion Collisions ◽  
Heavy Ion ◽  
Experimental Results ◽  
Relativistic Heavy Ion Collisions ◽  
Dense Medium ◽  
Medium Energy ◽  
Ion Collisions ◽  
Flavour Physics

In this proceedings, I present selected experimental results on heavy-flavour production at RHIC and at the LHC, which were presented at the Strangeness in Quark Matter 2017 conference. I will present a brief introduction to the heavy-flavour physics in heavy ion collisions and I will focus on recents measurements of in-medium energy loss and and collective properties of heavy-flavour particles, which provided important information on the mechanisms of heavy flavour interaction with the hot and dense medium created in ultra-relativistic heavy-ion collisions.

scholarly journals An Experimental Review on Heavy-Flavorv2in Heavy-Ion Collision

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Md. Nasim ◽  
Roli Esha ◽  
Huan Zhong Huang
Keyword(s):  
Hadron Collider ◽  
Large Mass ◽  
Heavy Ion ◽  
Azimuthal Anisotropy ◽  
Relativistic Heavy Ion Collisions ◽  
Dense Medium ◽  
Heavy Flavor ◽  
Relativistic Heavy Ion Collider ◽  
Ion Collisions ◽  
Ion Collision

For over a decade now, the primary purpose of relativistic heavy-ion collisions at the Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC) has been to study the properties of QCD matter under extreme conditions—high temperature and high density. The heavy-ion experiments at both RHIC and LHC have recorded a wealth of data in p+p, p+Pb, d+Au, Cu+Cu, Cu+Au, Au+Au, Pb+Pb, and U+U collisions at energies ranging fromsNN=7.7 GeV to 7 TeV. Heavy quarks are considered good probe to study the QCD matter created in relativistic collisions due to their very large mass and other unique properties. A precise measurement of various properties of heavy-flavor hadrons provides an insight into the fundamental properties of the hot and dense medium created in these nucleus-nucleus collisions, such as transport coefficient and thermalization and hadronization mechanisms. The main focus of this paper is to present a review on the measurements of azimuthal anisotropy of heavy-flavor hadrons and to outline the scientific opportunities in this sector due to future detector upgrade. We will mainly discuss the elliptic flow of open charmed meson (D-meson),J/ψ, and leptons from heavy-flavor decay at RHIC and LHC energy.

LOW-MASS ππ ENHANCEMENT IN BARYONIC ππ PRODUCTION: ABC EFFECT REVISED BY EXCLUSIVE MEASUREMENTS

2007 ◽  
Vol 22 (02n03) ◽  
pp. 625-628 ◽  
Author(s):  
◽  
M. Bashkanov ◽  
O. Khakimova ◽  
T. Skorodko ◽  
C. Bargholtz ◽  
...  
Keyword(s):  
Mass Spectrum ◽  
Invariant Mass ◽  
Bound States ◽  
Invariant Mass Spectrum ◽  
High Mass ◽  
Crucial Importance ◽  
Threshold Enhancement ◽  
Model Predictions ◽  
Low Mass ◽  
Mass Enhancement

The ABC effect - a puzzling threshold enhancement in the ππ invariant mass spectrum of double-pionic fusion to nuclear bound states - has been investigated since 40 years by inclusive measurements without providing a conclusive interpretation. First exclusive measurements to this topic have now been carried out at CELSIUS-WASA. They confirm a huge ππ threshold enhancement, prove it to be of scalar-isoscalar nature, i.e., a σ-channel phenomenon and reveal the theoretically predicted high-mass enhancement in inclusive spectra to be of πππ rather than of ππ nature - falsifying thus corresponding model predictions for the ABC effect. From the kinematically complete data samples we infer that the interaction between the two Δ particles created in this process is of crucial importance.

WHAT IS THE NATURE OF THE ABC EFFECT?

2011 ◽  
Vol 26 (03n04) ◽  
pp. 627-629
Author(s):  
◽  
M. BASHKANOV ◽  
H. CLEMENT
Keyword(s):  
Mass Spectrum ◽  
Total Cross Section ◽  
Invariant Mass ◽  
Cross Section ◽  
Pion Production ◽  
Invariant Mass Spectrum ◽  
Fusion Reactions ◽  
Nuclear Fusion Reactions ◽  
Low Mass ◽  
Mass Enhancement

The ABC effect — an intriguing low-mass enhancement in the ππ invariant mass spectrum — is known from inclusive measurements of two-pion production in nuclear fusion reactions. Exclusive measurements have been carried out at CELSIUS/WASA and WASA-at-COSY for the fusion reactions leading to d, 3 He and 4 He . They all reveal this effect to be of isoscalar nature and associated with a narrow Lorentzian-shaped structure in the total cross section. The latter could point to the formation of an isoscalar resonance, which couples to the pn channel as well as to an intermediate ΔΔ state.

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