Exotica production with ALICE

Abstract

Abstract. The high collision energies reached at the LHC lead to significant production yields of light (anti-)nuclei and (hyper-)nuclei in proton-proton, proton-lead and, in particular, lead-lead collisions. The excellent particle identification capabilities of the ALICE apparatus, based on the specific energy loss in the Time Projection Chamber and the velocity information in the Time-Of-Flight detector, allow for the detection of these rarely produced particles. Further, the Inner Tracking System gives the possibility to separate primary nuclei from those coming from weak decay of heavier systems.One example of such a weak decay is the measurement of the (anti-)hypertriton decay to 3 He + π − ( 3 He + π + ). The aforementioned capabilities of the ALICE apparatus offer the unique opportunity to search for exotica, like the bound state of a Λ and a neutron which would decay into a deuteron and a pion, or the bound state of two Λ's. Results on the production of stable nuclei in Pb-Pb collisions at √ s NN = 2.76 TeV are presented, and compared with thermal model predictions. We further present the current status of the searches, by their upper limits on the production yields, and compare the results to thermal and coalescence model expectations.

Production of light hypernuclei with light-ion beams and targets

“…Recently, exotic bound hypernuclei, like 2 Λ n and 3 Λ n, were extensively discussed and looked for in relativistic ion experiments [22,55]. As examples, we consider here the mesonic decay processes of 2 Λ n and 3 Λ n, i.e.…”

Formation of exotic baryon clusters in ultra-relativistic heavy-ion collisions

“…We believe that experiments should take into account this phase space structure in searching for novel exotic nuclear species (including anti-nuclei). In relativistic heavy ion collisions besides the recently observed 3 Λ H nuclei [1,3] other exotics (like ΛN, ΛNN) were under intensive discussions [6,39]. The extension of measurements into a new rapidity region will increase the yields of clusters in the data substantially.…”

“…Recently very encouraging results on the formation of exotic clusters come from experiments at relativistic colliders: For example, STAR at RHIC [1,2], and ALICE at LHC [3,4] have observed hyper-tritons and anti-hyper-tritons. Experimental programs to search for more heavy exotic nuclear species are now underway [5,6]. Therefore, a theoretical understanding of these phenomena is necessary.…”

Global variables and correlations: Summary of the results presented at the Quark Matter 2012 conference

“…A combined fit of 2010+2012 results gives: τ = 138 ± 23 60 ps [38]. Although ALICE extracts clear signals for 3 Λ H, 3 Λ H and 4 Λ He, no H-dibaryon peak is observed and therefore, upper limits on the yields of this hypothetical particle are derived [39].…”