Abstract
The enhancement in the dilepton spectrum observed in heavy-ion collisions for invariant electron-positron masses in the range \(0.15 GeV < M_{e^ + e^ - } < 0.6 GeV\) has recently been traced back to a corresponding enhancement in np collisions relative to pp collisions. Whereas the dilepton spectra in the latter are understood quantitatively, theoretical descriptions fail to describe the much higher dilepton rate in np collisions at beam energies below 2GeV, in particular regarding the region \(M_{e^ + e^ - } < 0.3 GeV\). We show that the missing strength can be attributed to ρ 0-channel π + π − production, which is dominated by the t-channel ΔΔ excitation and the recently found isoscalar dibaryonic resonance structure at 2.37 GeV. These processes do not contribute in pp collisions, but only in np collisions.
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References
DLS Collaboration (R.J. Porter et al.), Phys. Rev. Lett. 79, 1229 (1997).
DLS Collaboration (W.K. Wilson et al.), Phys. Rev. C 57, 1865 (1998).
HADES Collaboration (G. Agakichiev et al.), Phys. Lett. B 690, 118 (2010).
R. Shyam, U. Mosel, Phys. Rev. C 82, 062201 (2010).
J. Weil, H. van Hees, U. Mosel, Eur. Phys. J. A 48, 111 (2012) 48.
B.V. Martemyanov, M.I. Krivoruchenko, Amand Faessler, Phys. Rev. C 84, 047601 (2011).
E.L. Bratkovskaya, J. Aichelin, M. Thomere, S. Vogel, M. Bleicher, Phys. Rev. C 87, 064907 (2013).
L.P. Kaptari, B. Kämpfer, Nucl. Phys. A 764, 338 (2006).
PROMICE/WASA Collaboration (J. Johanson et al.), Nucl. Phys. A 712, 75 (2002).
PROMICE/WASA Collaboration (W. Brodowski et al.), Phys. Rev. Lett. 88, 192301 (2002).
PROMICE/WASA Collaboration (J. Pätzold et al.), Phys. Rev. C 67, 052202 (2003).
CELSIUS/WASA Collaboration (T. Skorodko et al.), Eur. Phys. J. A 35, 2008 (317).
CELSIUS/WASA Collaboration (T. Skorodko et al.), Phys. Lett. B 679, 30 (2009).
CELSIUS/WASA Collaboration (F. Kren et al.), Phys. Lett. B 684, 110 (2010) 702.
CELSIUS/WASA Collaboration (T. Skorodko et al.), Phys. Lett. B 695, 115 (2011).
CELSIUS/WASA Collaboration (T. Skorodko et al.), Eur. Phys. J. A 47, 108 (2011).
WASA-at-COSY Collaboration (P. Adlarson et al.), Phys. Lett. B 706, 256 (2011).
COSY-TOF Collaboration (S. Abd El-Bary et al.), Eur. Phys. J. A 37, 267 (2008).
COSY-TOF Collaboration (S. Abd El-Samad et al.), Eur. Phys. J. A 42, 159 (2009).
CELSIUS/WASA Collaboration (M. Bashkanov et al.), Phys. Rev. Lett. 102, 052301 (2009).
WASA-at-COSY Collaboration (P. Adlarson et al.), Phys. Rev. Lett. 106, 242302 (2011).
WASA-at-COSY Collaboration (P. Adlarson et al.), Phys. Lett. B 721, 229 (2013).
WASA-at-COSY Collaboration (P. Adlarson et al.), Phys. Rev. C 88, 055208 (2013).
L. Alvarez-Ruso, E. Oset, E. Hernandez, Nucl. Phys. A 633, 519 (1998).
Xu Cao, Bing-Song Zou, Hu-Shan Xu, Phys. Rev. C 81, 065201 (2010).
WASA-at-COSY Collaboration (P. Adlarson et al.), Phys. Rev. Lett. 112, 202301 (2014).
L.G. Dakhno et al., Sov. J. Nucl. Phys. 37, 540 (1983).
J. Bystricky et al., J. Phys. 48, 1901 (1987).
F. Dohrmann et al., Eur. Phys. J. A 45, 401 (2010).
G. Fäldt, C. Wilkin, Phys. Lett. B 701, 619 (2011).
M. Albadejo, E. Oset, Phys. Rev. C 88, 014006 (2013).
A. Gal, H. Garcilazo, Phys. Rev. Lett. 111, 172301 (2013).
A. Gal, H. Garcilazo, DOI:10.1016/j.nuclphysa.2014.02.019.
C.Q. Li, C.M. Ko, G.E. Brown, Phys. Rev. Lett. 75, 4007 (1995).
P. Koch, Z. Phys. C 57, 283 (1993).
Particle Data Group (J. Beringer et al.), Phys. Rev. D 86, 010001 (2012).
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Communicated by H. Ströher
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Bashkanov, M., Clement, H. On a possible explanation of the DLS puzzle. Eur. Phys. J. A 50, 107 (2014). https://doi.org/10.1140/epja/i2014-14107-9
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DOI: https://doi.org/10.1140/epja/i2014-14107-9