First measurement of low momentum dielectrons radiated off cold nuclear matter

Abstract

We present data on dielectron emission in proton induced reactions on a Nb target at 3.5 GeV kinetic beam energy measured with HADES installed at GSI. The data represent the first high statistics measurement of proton-induced dielectron radiation from cold nuclear matter in a kinematic regime, where strong medium effects are expected. Combined with the good mass resolution of 2%, it is the first measurement sensitive to changes of the spectral functions of vector mesons, as predicted by models for hadrons at rest or small relative momenta. Comparing the e+e invariant mass spectra to elementary p+p data, we observe for e+e momenta Pee < 0.8 GeV/c a strong modification of the shape of the spectrum, which we attribute to an additional rho-like contribution and a decrease of omega yield. These opposite trends are tentatively interpreted as a strong coupling of the rho meson to baryonic resonances and an absorption of the omega meson, which are two aspects of in-medium modification of vector mesons.

References in corpus (5)

• phi photo-production from Li, C, Al, and Cu nuclei at Egamma=1.5 - 2.4 GeV
• Modification of the rho meson detected by low-mass electron-positron pairs in central Pb-Au collisions at 158 A GeV/c
• Modification of the $\omega$-Meson Lifetime in Nuclear Matter
• Measurement of the in-medium phi-meson width in proton-nucleus collisions
• Nuclear mass number dependence of inclusive production of omega and phi mesons in 12 GeV p + A collisions

Cited by in corpus (10)

• Meson-nucleus potentials and the search for meson-nucleus bound states
• Lambda hyperon production and polarization in collisions of p(3.5 GeV) + Nb
• Medium effects in proton-induced $K^0$ production at 3.5 GeV
• Subthreshold Xi- Production in Collisions of p(3.5 GeV)+Nb
• ${\gamma }^{\ast }N\to N^{\ast }(1520)$ form factors in the timelike regime
• Holographically emulating sequential versus instantaneous disappearance of vector mesons in a hot environment
• Constraints on the kinetic mixing parameter ${\epsilon }^2$ for the light dark photons from dilepton production in heavy-ion collisions in the few-GeV energy range
• Effective spectral function of vector mesons via lifetime analysis
• Constraints on Kinetic Mixing of Dark Photons from Dilepton Spectra
• Velocity dependence of the mass modifications of $\rho$ and $\omega$ mesons in 12 GeV $p+A$ reactions