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arXiv · 1312.7397

Dielectron Mass Spectra from Au+Au Collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV

STAR Collaboration·L. Adamczyk·J. K. Adkins·G. Agakishiev·M. M. Aggarwal·Z. Ahammed·I. Alekseev·J. Alford·C. D. Anson·A. Aparin·D. Arkhipkin·E. C. Aschenauer·G. S. Averichev·A. Banerjee·D. R. Beavis·R. Bellwied·A. Bhasin·A. K. Bhati·P. Bhattarai·H. Bichsel·J. Bielcik·J. Bielcikova·L. C. Bland·I. G. Bordyuzhin·W. Borowski·J. Bouchet·A. V. Brandin·S. G. Brovko·S. Bültmann·I. Bunzarov·T. P. Burton·J. Butterworth·H. Caines·M. Calderóndze la Barca Sánchez·D. Cebra·R. Cendejas·M. C. Cervantes·P. Chaloupka·Z. Chang·S. Chattopadhyay·H. F. Chen·J. H. Chen·L. Chen·J. Cheng·M. Cherney·A. Chikanian·W. Christie·J. Chwastowski·M. J. M. Codrington·G. Contin·J. G. Cramer·H. J. Crawford·X. Cui·S. Das·A. Davila Leyva·L. C. De Silva·R. R. Debbe·T. G. Dedovich·J. Deng·A. A. Derevschikov·R. Derradi de Souza·S. Dhamija·B. di Ruzza·L. Didenko·C. Dilks·F. Ding·P. Djawotho·X. Dong·J. L. Drachenberg·J. E. Draper·C. M. Du·L. E. Dunkelberger·J. C. Dunlop·L. G. Efimov·J. Engelage·K. S. Engle·G. Eppley·L. Eun·O. Evdokimov·R. Fatemi·S. Fazio·J. Fedorisin·P. Filip·E. Finch·Y. Fisyak·C. E. Flores·C. A. Gagliardi·D. R. Gangadharan·D. Garand·F. Geurts·A. Gibson·M. Girard·S. Gliske·L. Greiner·D. Grosnick·D. S. Gunarathne·Y. Guo·A. Gupta·S. Gupta·W. Guryn
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Abstract

We report the STAR measurements of dielectron ($e^+e^-$) production at midrapidity ($|y_{ee}|<$1) in Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 200\,GeV. The measurements are evaluated in different invariant mass regions with a focus on 0.30-0.76 ($\rho$-like), 0.76-0.80 ($\omega$-like), and 0.98-1.05 ($\phi$-like) GeV/$c^{2}$. The spectrum in the $\omega$-like and $\phi$-like regions can be well described by the hadronic cocktail simulation. In the $\rho$-like region, however, the vacuum $\rho$ spectral function cannot describe the shape of the dielectron excess. In this range, an enhancement of 1.77$\pm$0.11(stat.)$\pm$0.24(sys.)$\pm$0.33(cocktail) is determined with respect to the hadronic cocktail simulation that excludes the $\rho$ meson. The excess yield in the $\rho$-like region increases with the number of collision participants faster than the $\omega$ and $\phi$ yields. Theoretical models with broadened $\rho$ contributions through interactions with constituents in the hot QCD medium provide a consistent description of the dilepton mass spectra for the measurement presented here and the earlier data at the Super Proton Synchrotron energies.

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STAR Collaboration, L. Adamczyk, J. K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, C. D. Anson, A. Aparin, D. Arkhipkin, E. C. Aschenauer, G. S. Averichev, A. Banerjee, D. R. Beavis, R. Bellwied, A. Bhasin, A. K. Bhati, P. Bhattarai, H. Bichsel, J. Bielcik, J. Bielcikova, L. C. Bland, I. G. Bordyuzhin, W. Borowski, J. Bouchet, A. V. Brandin, S. G. Brovko, S. Bültmann, I. Bunzarov, T. P. Burton, J. Butterworth, H. Caines, M. Calderóndze la Barca Sánchez, D. Cebra, R. Cendejas, M. C. Cervantes, P. Chaloupka, Z. Chang, S. Chattopadhyay, H. F. Chen, J. H. Chen, L. Chen, J. Cheng, M. Cherney, A. Chikanian, W. Christie, J. Chwastowski, M. J. M. Codrington, G. Contin, J. G. Cramer, H. J. Crawford, X. Cui, S. Das, A. Davila Leyva, L. C. De Silva, R. R. Debbe, T. G. Dedovich, J. Deng, A. A. Derevschikov, R. Derradi de Souza, S. Dhamija, B. di Ruzza, L. Didenko, C. Dilks, F. Ding, P. Djawotho, X. Dong, J. L. Drachenberg, J. E. Draper, C. M. Du, L. E. Dunkelberger, J. C. Dunlop, L. G. Efimov, J. Engelage, K. S. Engle, G. Eppley, L. Eun, O. Evdokimov, R. Fatemi, S. Fazio, J. Fedorisin, P. Filip, E. Finch, Y. Fisyak, C. E. Flores, C. A. Gagliardi, D. R. Gangadharan, D. Garand, F. Geurts, A. Gibson, M. Girard, S. Gliske, L. Greiner, D. Grosnick, D. S. Gunarathne, Y. Guo, A. Gupta, S. Gupta, W. Guryn. 2013-12-28. Dielectron Mass Spectra from Au+Au Collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV. https://doi.org/10.1103/physrevlett.113.022301

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