Nuclearite search with the ANTARES neutrino telescope Vlad Popa, for the ANTARES Collaboration Institute for Space Sciences, Bucharest – Magurele, Romania

Aggregates of u, d, s quarks + electrons, n e = 2/3 n u –1/3 n d –1/3 n s Ground state of QCD; stable for  300 < A < Nuclearites: basic properties E. Witten, Phys. Rev. D30 (1984) 272A. De Rujula, S. L. Glashow, Nature 312 (1984) 734 Produced in Early Universe or in strange star collisions (J. Madsen, PRD71 (2005) ) Candidates for cold Dark Matter! Searched for in CR reaching the Earth R (fm) M (GeV) A qualitative picture… [black points are electrons]  N  3.5 x g cm -3  nuclei  g cm -3

Typical galactic velocities   Dominant interaction: elastic collisions with atoms in the medium Dominant energy losses: Phenomenological flux limit from the local density of DM:

Arrival conditions to the depth of ANTARES After a propagation path L in a medium, the velocity of a nuclearite of initial velocity v 0 becomes: in the atmosphere: a = 1.2  g cm -3 ; b = 8.6  10 5 cm; H  50 km (T. Shibata, Prog. Theor. Phys. 57 (1977) 882.) in water:  w  1 g cm -3

Intermediate mass nuclearites M (GeV) s e d u u u u u d d d s d s s s e e e - Essentially neutral (most if not all e - inside) - “Simple” properties: galactic velocities, elastic collisions, energy losses… - Could reach ANTARES from above - Better flux limit from MACRO: M. Ambrosio et al., Eur.Phys. J. C13 (2000) 453; L. Patrizii, TAUP Two low masses to reach ANTARES Could traverse the Earth, but very low expected fluxes

A little more on dE/dx… For M  8.4  GeV it depends only on v 2 The passage of a nuclearite in matter produces heat along its path In transparent media some of the energy dissipated could appear as visible light (black body radiation) The “optical efficiency” = the fraction of dE/dx appearing as light in water estimated to be  = 3  (lower bound) (A. De Ruhula, S.L. Glashow, Nature 312 (1984) 734)

Velocities in ANTARES 2100 m 2274 m 2448 m Example for vertical incidence

Light production / cm of path  starts to increase Example for vertical incidence

General strategy in ANTARES: “all data to shore”. The basic info: the “hit”: time and charge information of a photon detected by a PMT If the charge (amplitude) is above a pre- defined threshold, -> “L0” hit, buffered in a 2.2  s window.

General strategy in ANTARES: “all data to shore”. If the charge (amplitude) is above a pre- defined threshold, -> “L0” hit, buffered in a 2.2  s window. Local coincidence: “L1”. Two L0 hits in the same storey within 20 ns, or a single large amplitude hit (3 pe or more) The “directional trigger” (DT): at least 5 L1 hits anywhere in the detector, within a 2.2  s window and causally connected. “T3 cluster”: two “L1” hits in adjacent or next-to-adjacent storeys within 20 ns. The “cluster trigger” (CT): at least two T3 within 2.2  s.

General strategy in ANTARES: “all data to shore”. All PMT pulses in a 2.2  s window conserved in a buffer, as well as the previous window. When a trigger occurs (DT or/and CT), all hits (above threshold) from the corresponding time window as well as the previous one are recorded for off-line analysis. The shortest duration of an “event” (“snapshot”) is thus 4.4  s; as triggers could occur in the next time window, snapshots could be longer (adjacent events are merged). Nuclearites are expected to be slowly moving: should be seen as anomalously long events, or as series of consequent snapshots. The typical crossing time about 1 ms!

Nuclearite search in ANTARES, 2007 and 2008 data Data recorded during ANTARES completion Various detector configurations (5, 9, 10 and 12 lines) Variations in the bioluminescence background Different threshold values Each configuration treated separately! Blind analysis: the search strategy defined trough Monte Carlo, validated using 15% of each data set, analysis on all data after unblinding maximized efficiency

Monte Carlo simulations Nuclearites: Chose the mass and initial velocity, compute the velocity at the entry in the simulation hemisphere, propagate in the hemisphere with time resolution of 2 ns Geometrical acceptance Events, mixed with background and processed by DT and CT triggers Efficiencies Background: -Atmospheric muons: MUPAGE (M. Bazzoti et al., Comput. Phys. Commun, 181 (2010) 835) - Bioluminiscence, K, etc, extracted from real runs.

Selection criterion: the duration of the events, dt = t last trigg. – t first trigg. Triggers optimized for relativistic particles → most simulated events produce multiple adjacent snapshots! “C1” cut For single snapshot events we require dt > 2C1 (Cut “C2”)

No event survived the C1 (+C2) cuts applied to 15% of the data collected during 2007 and Analysis sensitivities' obtained for all configurations.

After unblinding, data from 2007 and 2008 were analyzed. Very few events survived the cuts. Each was carefuly analized: - check of the Event Display - study of the collected charge barycenter versus time. As the light emitted by the over-heated nuclearite path is isotropic, this should describe the e vent topology (a first step event reconstruction). No event compatible with the down-going nuclearite predictions. All events interpretable as bioluminescent phenomena. We could derive the 90% upper flux limit for down-going nuclearites,