V. S. Berezinsky

Muon ''depth-intensity'' relation measured by the LVD underground experiment and cosmic-ray muon spectrum at sea level

We present the analysis of the muon events with all muon multiplicities collected during 21804 hours of operation of the first LVD tower. The measured angular distribution of muon intensity has been converted to the `depth -- vertical intensity relation in the depth range from 3 to 12 km w.e.. The analysis of this relation allowed to derive the power index,

The large-volume detector (LVD) of the Gran Sasso Laboratory

gamma

Superdense cosmological dark matter clumps

, of the primary all-nucleon spectrum:

On the possibility of a two-bang supernova collapse

gamma=2.78 pm 0.05

Hidden source of high-energy neutrinos in collapsing galactic nucleus

. The `depth -- vertical intensity relation has been converted to standard rock and the comparison with the data of other experiments has been done. We present also the derived vertical muon spectrum at sea level.

The limit to the UHE extraterrestrial neutrino flux from the observations of horizontal air showers at EAS-TOP

SummaryWe describe here the LVD experiment (Large-Volume Detector) of the Gran Sasso Laboratory, which is the natural improvement of the LSD experiment (Liquid Scintillation Detector) running in the Mont Blanc Laboratory. The LVD ((31×13) m2 area, height 12 m) consists of ≈1800 tons of liquid scintillator and of a system of streamer tubes on 5 layers for reconstructing tracks of charged particles. As any experiment in an underground laboratory, which has a low statistics of events and requires long running times, the LVD is a multipurpose experiment but with different priorities of the researches. The main goal is neutrino astronomy, firstly detection of neutrinos from collapsing stars and secondly high-energy neutrinos and solar neutrinos. Since the expected number of interactions of neutrinos, from a stellar collapse is very high (of order of 900 for a collapse at the distance of the galactic centre), the LVD is, contrary to the present experiments, a real neutrino observatory, able to make a detailed analysis of the energy and temporal distributions of the burst. In addition to neutrino astrophysics, with the LVD experiment excellent possibilities exist to perform researches in cosmic-ray and high-energy elementary-particle physics.RiassuntoSi descrive lesperimento LVD (Large Volume Detector) del laboratorio del Gran Sasso, che rappresenta il naturale sviluppo dellesperimento LSD (Liquid Scintillation Detector) in funzione nel laboratorio del Monte Bianco. LVD (area (31×13) m2, altezza 12 m) consiste di ∼1800 tonnellate di scintillatore liquido e di un sistema di tubi a streamer su 5 piani per la ricostruzione delle tracce di particelle cariche. Come tutti gli esperimenti in laboratori sotterranei, che sono a tempi lunghi ed a bassa statistica, lesperimento LVD è a multiscopi ma con diverse priorità delle ricerche. Lobiettivo principale è lastronomia neutrinica, in primo luogo la rivelazione di neutrini da collassi gravitazionali stellari, e poi neutrini di alta energia e neutrini solari. Dato lalto numero previsto di interazioni di neutrini (∼900 per un collasso alla distanza del centro galattico) da stelle collassanti, lesperimento LVD costituisce, a differenza degli attuali esperimenti, un vero e proprio osservatorio neutrinico, in grado di compiere unanalisi dettagliata delle distribuzioni energetica e temporale del burst. Oltre allastrofisica neutrinica, con lesperimento LVD si possono compiere ricerche in fisica della radiazione cosmica e di particelle elementari ad altissime energie.РезюмеВ данной работе описывается зксперимент LVD (Large Volume Detector), который будет проводиться в лаборатории Гран Cacco. LVD является естественным продолжением эксперимента LSD (Liquid Scintillation Detector) в лаборатории Монблан. LVD (площадь (31×13) м2, высота 12 м) содержит 1800 тонн жидкого сцинтиллятора и включает в себя систему стримерных детекторов, размещенных на 5 уровнях. Последние используются для реконструкции треков заряженных частиц. Как и любой длительный эксперимент в подземных условиях, когда статистика событий невелика, LVD имеет многоцелевое назначение. Научные программы, однако, будут обладать различным приоритетом. Основное внимание будет уделяться нейтринной астрономии, и в первую очередь— детектированию нейтрино от коллапсирующих звезд. Кроме того, будут проводиться исследования по регистрации нейтрино высоких энергий и солнечных нейтрино. Поскольку ожидаемое количество взаимодействий в случае прихода потока нейтрино от коллапса очень велико, порядка 900, LVD будет настоящей нейтринной обсерваторией, способной, в отличие от ведущихся сейчас экспериментов, детально исследовать энергетическое временное распределения для вспышки нейтринного излучения. В дополнение к нейтринной астрофизике, имеются очень хорошие перспективы и для исследований в области космических лучей и физики элементарных частиц высоких энергий.

Upper limit on the prompt muon flux derived from the LVD underground experiment

V. Berezinsky, 2, 3 V. Dokuchaev, 3 Yu. Eroshenko, 3 M. Kachelrieß, and M. Aa. Solberg INFN, Laboratori Nazionali del Gran Sasso, I–67010 Assergi (AQ), Italy Center for Astroparticle Physics at LNGS (CFA), I–67010 Assergi (AQ), Italy Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, Russia Institutt for fysikk, NTNU Trondheim, N–7491 Trondheim, Norway (Dated: February 18, 2010)

Formation and internal structure of superdense dark matter clumps and ultracompact minihaloes

SummaryThe possibility of a two-bang stellar collapse originating SN 1987a, and having the characteristics of the events recorded in Mont Blanc and Kamiokande, is discussed here. According to the «standard» collapse models of nonrotating stars, which predict the formation of a neutrinosphere with a nondegenerate neutrino gas inside the star, the Mont Blanc and Kamiokande data for the first burst give a too large stellar mass. On the contrary, a degenerate neutrino gas with low temperatureT≈0.5 MeV, and chemical potential μ≈(12÷15), predicts a relatively low total energy outflowWν≈(2÷6)·1054 erg, and a small number of expected interactions in Kamiokande. A possible scenario is suggested: a massive (M≈20M⊙) rotating star is fragmented into two pieces, one light and the other heavy, at the onset of the collapse. The massive component collapses to a black hole, and produces the first burst. Neutrinos are trapped inside the collapsing star because of elastic scattering in the outer core off heavy nuclei, withA≳300. It is shown that neutrinos fill up the quantum states, producing a degenerate neutrino gas. The second burst is explained by coalescence of the light fragment (M≈(1÷3)M⊙) onto the massive black hole. The time delay between the two observed bursts (4.7 h) is mostly connected with gravitational braking, when the light fragment falls down onto the black hole, with an accompanying emission of gravitational waves for times of order of hours.RiassuntoSi discute la possibilità che la supernova 1987a abbia avuto origine da un collasso a due stadi, avente le caratteristiche degli eventi registrati nellOsservatorio Neutrinico del Monte Bianco e nellesperimento di Kamioka. Secondo i modelli «standard» di collasso di stelle senza rotazione, che prevedono la formazione di una neutrinosfera con un gas non degenere di neutrini al suo interno, i dati del Monte Bianco e di Kamioka per il primo burst comportano un valore troppo alto della massa stellare. Al contrario, un gas degenere di neutrini a bassa temperatureT∼0.5 MeV e con potenziale chimico μ∼(12÷15) comporta unemissione totale in neutrini relativamente bassaWν∼(2÷6)·1054 erg ed un piccolo numero di interazioni in Kamiokande. Si suggerisce un possibile scenario: una stella massiva (M∼20M⊙) in rotazione si frammenta in due oggetti, uno leggero e laltro pesante, allinizio del collasso. Loggetto massivo collassa in un buco nero e produce il primo burst. I neutrini vengono intrappolati entro la stella collassante a causa dello scattering elastico nel core esterno dovuto a nuclei pesanti, conA≳300. Si mostra che i neutrini riempiono gli stati quantici, producendo un gas degenere di neutrini. Il secondo burst è spiegato dalla caduta del frammento leggeroM∼(1÷3)M⊙ sul black hole massivo.РезюмеВ работе обсуждается возможность коллапса сверхновой SN 1987a, характеризующегося двумя взрывами и имеющего особенности, зарегистрированные на Мон Блане и в Камиоканде. Согласно «стандартным» моделям коллапса невращающихся звезд, которые предсказывают образование нейтринной сферы с невырожденными нейтринным газом внутри звезды, данные на Мон Блане и в Камиоканде для первой вспышки дают слишком большую массу звезды. Напротив, вырожденный нейтринный газ с низкой температуройT≈0.5 МэВ и химическим потенциалом μ≈12÷15 предсказывает выход относительно малой полной энергииWν≈(2÷6)·1054 эрг и малое число ожидаемых взаимодействий в Камиоканде. Предлагается возможный сценарий: массивная (M≈20M⊙) врашаюшаяся звезда разделяется на две части, одна легкая и другая тяжелая, в начале коллапса. Массивная компонента коллапсирует в черную дыру и производит первую вспышку. Нейтрино захватывются внутри коллапсируыщей звезэы вследствие упругого рассеяния во внешней оболочке на тяжелых ядрах сA≥300. Показывается, что нейтрино заполняют квантовые состояния, обраяуя вырожденный нейтринный газ. Вторая вспышка объясняется коалесцией легкого фрагмента (M∼(1÷3)M⊙) с массивной черной дырой. Время запаздывания между двумя наблюденными вспышками (4.7 часа) в основном связывается с гравитационным торможением, колэа легкий фрагмент падает на черную дыру, что сопровождается излучением гравитационных вплн в течение времени, порядка несколъких часов.

Annihilations of superheavy dark matter in superdense clumps

Abstract We propose a model of a short-lived very powerful source of high energy (HE) neutrinos. It is formed as a result of the dynamical evolution of a galactic nucleus prior to its collapse into a massive black hole and formation of high-luminosity AGN. This stage can be referred to as “pre-AGN”. A dense central stellar cluster in the galactic nucleus at the late stage of evolution consists of compact stars (neutron stars and stellar mass black holes). This cluster is sunk deep into the massive gas envelope produced by destructive collisions of a primary stellar population. Frequent collisions of neutron stars in a central stellar cluster are accompanied by the generation of ultrarelativistic fireballs and shock waves. These repeating fireballs result in a formation of the expanding rarefied cavity inside the envelope. The charged particles are effectively accelerated in the cavity and, due to pp collisions in the gas envelope, they produce HE neutrinos. All HE particles, except neutrinos, are absorbed in the thick envelope. The duration of this pre-AGN phase is ∼1 year, the number of the sources can be a few per cosmological horizon. HE neutrino signal can be detected by underground neutrino telescope with effective area S∼1 km2.We propose the model of a short-lived very powerful source of high energy neutrinos. It is formed as a result of the dynamical evolution of a galactic nucleus prior to its collapse into a massive black hole and formation of high-luminosity AGN. This stage can be referred to as ``pre-AGN. A dense central stellar cluster in the galactic nucleus on the late stage of evolution consists of compact stars (neutron stars and stellar mass black holes). This cluster is sunk deep into massive gas envelope produced by destructive collisions of a primary stellar population. Frequent collisions of neutron stars in a central stellar cluster are accompanied by the generation of ultrarelativistic fireballs and shock waves. These repeating fireballs result in a formation of the expanding rarefied cavity inside the envelope. The charged particles are effectively accelerated in the cavity and, due to pp-collisions in the gas envelope, they produce high energy neutrinos. All high energy particles, except neutrinos, are absorbed in the thick envelope. Duration of this pre-AGN phase is about 10 yr, the number of the sources can be ~ 10 per cosmological horizon. High energy neutrino signal can be detected by underground neutrino telescope with effective area ~1 km^2.

Study of single muons with the Large Volume Detector at the Gran Sasso Laboratory

Abstract Extensive Air Showers at large zenith angles θ > 70° (Horizontal Air Showers, HAS) are observed at the EAS-TOP array at Campo Imperatore (Gran Sasso Laboratories). The rate of these events exceeds the one due to primary cosmic rays (at this angles) and therefore these showers have to be generated by penetrating particles. Assuming that they are produced by atmospheric muons we derived the muon flux as Fμ(> 30 TeV) = 1.1 × 10−11cm−2s−1sr−1, in good agreement with the underground measurements. The upper limits for diffuse neutrino radiation from these measurements is Iν(> 105GeV) dI ν e (E 0 )/dE ν e −18 cm −2 s −1 sr −1 GeV −1 , for the resonant ( E 0 = m W 2 2m e = 6.4 × 10 6 GeV ) neutrinos.