Inclusive meson production in 3.5 GeV pp collisions studied with the HADES spectrometer

Abstract

Abstract.We present the inclusive di-electron invariant-mass spectrum from p+p interactions at 3.5 GeV kinetic beam energy. It is a very important reference for the study of vector meson production off the nucleus, recently investigated by HADES in p+ 93 Nb reactions at the same beam energy. Up to invariant masses of 0.6 GeV/c 2 the main contributions to the e + e − spectrum are π 0 , η, ω and ∆ Dalitz decays. In the vector-meson region a clear peak corresponding to the ω direct decay is reconstructed with ≈2% mass resolution. Subtracting this peak from the spectrum allows to investigate additional sources, in particular the ρ meson. Indeed, the latest results from HSD and UrQMD calculations show different distributions for the shape of the ρ meson at these energies. Therefore it is important to experimentally understand the production mechanism of the ρ meson in elementary reactions. Besides the spectral shape of the mesons, their inclusive production cross sections are also not known at these energies. Due to the large and flat acceptance of the HADES spectrometer for e + e − masses above 0.2 GeV/c 2 and for P T < 1GeV/c, acceptance corrections are to a large extent model independent. This allows us to extract the preliminary inclusive cross section values for the meson productions at these energies.

Inclusive dielectron spectra in p+p collisions at 3.5 GeV kinetic beam energy

“…For instance, as discussed in [4], implementation of the Iachello model [15] enhances dielectron yield in the high-mass region. This has also been demonstrated in [25,51]. We expect hence that our data can help to clarify the issue of form factors in the Δ(1232) Dalitz decay and the role of other baryon resonances, as mentioned in the introduction.…”

“…In the experiment (see [1] for a detailed description of HADES), a proton beam of 10 7 particles/s with a kinetic energy of 3.5 GeV was incident on a 4.4 cm long liquidhydrogen target [17]. The data readout was started upon 4 We use the following convention of the squared 4-momenta: a first-level trigger (LVL1) decision.…”

Possible Studies at the First Stage of the NICA Collider Operation with Polarized and Unpolarized Proton and Deuteron Beams

“…[123] and references therein. The ρ 0 inclusive cross section has been measured at different accelerators since the 70s, mostly at CERN [124], and more recently by the HADES collaboration [125]. In Ref.…”

In-Medium Properties of Vector Mesons in a Transport Approach

“…Fig. 1 shows a comparison plot of a GiBUU simulation to HADES data [23] for a proton beam of 3.5 GeV kinetic energy impinging on a fixed proton target. This setup corresponds to a centerof-mass energy of √ s = 3.18 GeV.…”