Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 1806.02295

Low-$p_T$ $e^{+}e^{-}$ pair production in Au$+$Au collisions at $\sqrt{s_{NN}}$ = 200 GeV and U$+$U collisions at $\sqrt{s_{NN}}$ = 193 GeV at STAR

J. Adam·L. Adamczyk·J. R. Adams·J. K. Adkins·G. Agakishiev·M. M. Aggarwal·Z. Ahammed·N. N. Ajitanand·I. Alekseev·D. M. Anderson·R. Aoyama·A. Aparin·D. Arkhipkin·E. C. Aschenauer·M. U. Ashraf·F. Atetalla·A. Attri·G. S. Averichev·X. Bai·V. Bairathi·K. Barish·A. J. Bassill·A. Behera·R. Bellwied·A. Bhasin·A. K. Bhati·J. Bielcik·J. Bielcikova·L. C. Bland·I. G. Bordyuzhin·J. D. Brandenburg·A. V. Brandin·D. Brown·J. Bryslawskyj·I. Bunzarov·J. Butterworth·H. Caines·M. Calderón de la Barca Sánchez·J. M. Campbell·D. Cebra·I. Chakaberia·P. Chaloupka·F-H. Chang·Z. Chang·N. Chankova-Bunzarova·A. Chatterjee·S. Chattopadhyay·J. H. Chen·X. Chen·J. Cheng·M. Cherney·W. Christie·G. Contin·H. J. Crawford·S. Das·T. G. Dedovich·I. M. Deppner·A. A. Derevschikov·L. Didenko·C. Dilks·X. Dong·J. L. Drachenberg·J. C. Dunlop·L. G. Efimov·N. Elsey·J. Engelage·G. Eppley·R. Esha·S. Esumi·O. Evdokimov·J. Ewigleben·O. Eyser·R. Fatemi·S. Fazio·P. Federic·P. Federicova·J. Fedorisin·P. Filip·E. Finch·Y. Fisyak·C. E. Flores·L. Fulek·C. A. Gagliardi·T. Galatyuk·F. Geurts·A. Gibson·D. Grosnick·D. S. Gunarathne·Y. Guo·A. Gupta·W. Guryn·A. I. Hamad·A. Hamed·A. Harlenderova·J. W. Harris·L. He·S. Heppelmann·N. Herrmann·A. Hirsch·L. Holub
View original source ↗Read source document ↗Export metadata ↓

Abstract

We report first measurements of $e^{+}e^{-}$ pair production in the mass region 0.4 $<M_{ee}<$ 2.6 GeV/$c^{2}$ at low transverse momentum ($p_T<$ 0.15 GeV/$c$) in non-central Au$+$Au collisions at $\sqrt{s_{NN}}$ = 200 GeV and U$+$U collisions at $\sqrt{s_{NN}}$ = 193 GeV. Significant enhancement factors, expressed as ratios of data over known hadronic contributions, are observed in the 40-80% centrality of these collisions. The excess yields peak distinctly at low-$p_T$ with a width ($\sqrt{\langle p^2_T\rangle}$) between 40 to 60 MeV/$c$. The absolute cross section of the excess depends weakly on centrality while those from a theoretical model calculation incorporating an in-medium broadened $\rho$ spectral function and radiation from a Quark Gluon Plasma or hadronic cocktail contributions increase dramatically with increasing number of participant nucleons. Model calculations of photon-photon interactions generated by the initial projectile and target nuclei describe the observed excess yields but fail to reproduce the $p^{2}_{T}$ distributions.

Explore related subjects

hep-exnucl-ex

Keep this discovery

BibTeXRIS

J. Adam, L. Adamczyk, J. R. Adams, J. K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, N. N. Ajitanand, I. Alekseev, D. M. Anderson, R. Aoyama, A. Aparin, D. Arkhipkin, E. C. Aschenauer, M. U. Ashraf, F. Atetalla, A. Attri, G. S. Averichev, X. Bai, V. Bairathi, K. Barish, A. J. Bassill, A. Behera, R. Bellwied, A. Bhasin, A. K. Bhati, J. Bielcik, J. Bielcikova, L. C. Bland, I. G. Bordyuzhin, J. D. Brandenburg, A. V. Brandin, D. Brown, J. Bryslawskyj, I. Bunzarov, J. Butterworth, H. Caines, M. Calderón de la Barca Sánchez, J. M. Campbell, D. Cebra, I. Chakaberia, P. Chaloupka, F-H. Chang, Z. Chang, N. Chankova-Bunzarova, A. Chatterjee, S. Chattopadhyay, J. H. Chen, X. Chen, J. Cheng, M. Cherney, W. Christie, G. Contin, H. J. Crawford, S. Das, T. G. Dedovich, I. M. Deppner, A. A. Derevschikov, L. Didenko, C. Dilks, X. Dong, J. L. Drachenberg, J. C. Dunlop, L. G. Efimov, N. Elsey, J. Engelage, G. Eppley, R. Esha, S. Esumi, O. Evdokimov, J. Ewigleben, O. Eyser, R. Fatemi, S. Fazio, P. Federic, P. Federicova, J. Fedorisin, P. Filip, E. Finch, Y. Fisyak, C. E. Flores, L. Fulek, C. A. Gagliardi, T. Galatyuk, F. Geurts, A. Gibson, D. Grosnick, D. S. Gunarathne, Y. Guo, A. Gupta, W. Guryn, A. I. Hamad, A. Hamed, A. Harlenderova, J. W. Harris, L. He, S. Heppelmann, N. Herrmann, A. Hirsch, L. Holub. 2018-06-06. Low-$p_T$ $e^{+}e^{-}$ pair production in Au$+$Au collisions at $\sqrt{s_{NN}}$ = 200 GeV and U$+$U collisions at $\sqrt{s_{NN}}$ = 193 GeV at STAR. https://doi.org/10.1103/physrevlett.121.132301

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Production of Light Nuclei and Hypernuclei in Heavy-Ion Collisions

We review recent STAR and ALICE measurements of light-nucleus and hypernucleus yields, femtoscopic correlations, and collective flow presented at SQM 2026. Statistical-hadronization calculations provide a useful baseline for integrated yields but do not simultaneously describe all measured light-nucleus ratios across collision energies and system sizes. For bound states with mass number $A<4$, current coalescence calculations provide a broadly consistent description of yields, femtoscopic correlations, and collective flow, although the quantitative hypertriton comparison depends on the assumed few-body wave function. The suppressed production of resonant $^{4}$Li relative to compact $^{4}$He indicates an effect of nuclear structure and late-stage dynamics. However, the quantitative model comparison also depends on the treatment of feed-down from unstable states. In high-multiplicity $p$+$p$ collisions, pion-deuteron femtoscopy further indicates that most observed (anti)deuterons are formed through nucleon fusion after strong decays of short-lived resonances. Taken together, these measurements show that production chronology and internal nuclear structure leave measurable imprints on the physics observables.

hep-ex↗
arXiv2026

Search for the process $e^+e^-\to f_1(1285)$ at the SND detector

In the experiment with the SND detector at the VEPP-2000 $e^+e^-$ collider, a search is performed for the direct production of the $C$-even $f_1(1285)$ resonance in $e^+e^-$ collisions. The analysis is based on data with an integrated luminosity of about 200 pb$^{-1}$, accumulated in the center-of-mass energy range of 1.14--1.46 GeV, of which about 72 pb$^{-1}$ were recorded near the maximum of the $f_1(1285)$ resonance. The $f_1(1285)$ production cross section at the resonance maximum $\sigma(e^+e^-\to f_1)=(31\pm 13\pm 2)$ pb and the branching fraction $B(f_1(1285)\to e^+e^-)=(3.5\pm 1.4\pm 0.3)\times 10^{-9}$ have been measured. The significance of the observation of the $e^+e^-\to f_1(1285)$ process is $2.5\sigma$. Since the significance is low, we also present the upper limits at the 90% confidence level: $\sigma(e^+e^-\to f_1)<48\mbox{ pb}$ and $B(f_1(1285)\to e^+e^-)<5.4\times 10^{-9}$.

hep-ex↗
arXiv2026

Projected Sensitivity to Slow Muonphilic Dark Matter with Accelerator Muon Beams

The nature of dark matter (DM) remains one of the most enduring open questions in modern physics, and muonphilic DM has emerged as a promising scenario that complements traditional DM candidates. Following the recently established cosmic-ray muon scattering approach, we investigate the sensitivity for probing slow muonphilic DM with accelerator muon beams. A Geant4-based simulation framework is developed, incorporating the detector geometry from the PKMu muon tomography system and a dedicated elastic $\mu$-DM scattering process. The projected sensitivity is found to be largely insensitive to both the beam energy and the transverse beam size when the beam is fully contained within the detector acceptance. For a benchmark beam intensity of $10^5/\rm{s}$, the simulated pure-muon beam surpasses the existing cosmic-ray limit of $1.61\times10^{-17}$ cm$^2$ at $m_{\rm DM}=1$ GeV within approximately 11 seconds. A realistic muon beam phase-space distribution based on simulations for the High Intensity heavy-ion Accelerator Facility (HIAF) is also implemented, yielding projected limits that improve upon the cosmic-ray results by nearly two orders of magnitude in a one-day exposure. These results demonstrate that a beam-muon scattering experiment offers a robust and promising route toward significantly improved sensitivity to slow muonphilic DM.

hep-ex↗