Nuclearite search with the MACRO detector at Gran Sasso

In this paper we present the results of a search for nuclearites in the penetrating cosmic radiation using the scintillator and track-etch subdetectors of the MACRO apparatus. The analyses cover the range at the detector depth (3700 {\rm hg/cm^2}) ; for the flux limit is for an isotropic flux of nuclearites, and twice this value for a flux of downgoing nuclearites. Received: 4 May 1999 / Published online: 25 February 2000     

MACRO, a large-area detector at the Gran Sasso Laboratory

Summary MACRO is a large-area detector to be installed in hall B of the Gran Sasso Laboratory. Making use of scintillation counters, plastic streamer tubes, and track-etch detectors, it is designed to search for superheavy magnetic monopoles beyond the Parker bound, high-energy gamma and neutrino cosmic sourcs, and, more in general, exotic phenomena in the cosmic radiation. MACTO is an acronym for Monopole, Astrophysics and Cosmic Ray Observatory. The present collaboration: Bari(**)C. De Marzo, O. Erriquez, N. Giglietto andF. Posa. Bologna(**):M. Attolini, F. Baldetti, G. Giacomelli, F. Grianti, A. Margiotta andP. Serra. Caltech:B. Barish, C. Lane andG. Liu. CERN:P. Musset, G. Poulard andH. Sletten. Drexel:R. Steinberg. Laboratori Nazionali di Frascati dell'INFN:G. Battistoni, H. Bilokon, C. Bloise, P. Campana, V. Chiarella, A. Ciocio, A. Grillo, E. Iarocci, A. Marini, A. Rindi, F. Ronga, L. Satta, M. Spinetti, L. Trasatti andV. Valente. Indiana:S. Ahlen, B. Brabson, R. Heinz, S. Mufson, H. Ogren andP. Smith. Michigan:J. Musser, J. Stone, L. Sulak andG. Tarlé. Pisa(**):C. Angelini, A. Baldini, C. Bemporad, A. Cnops, V. Flaminio, G. Giannini, R. Pazzi andB. Saitta. Roma(**):G. Auriemma, M. De Vincenzi, E. Lamanna, G. Martellotti, S. Petrera, L. Petrillo, P. Pistilli, G. Rosa, A. Sciubba andM. Severi. Texas A&M:R. Webb. Torino:M. Arneodo, G. Borreani, P. Giubellino, F. Marchetto, A. Marzari, S. Palestini andL. Ramello.Virginia Tech:S. Torres andP. Trower. (**) Sezione INFN e Dipartimento di Fisica dell'Università.     

Search for massive rare particles with the MACRO track-etch detector at Gran Sasso

Searches for massive penetrating particles in the cosmic radiation have been performed with the MACRO nuclear track detector used as a “stand alone” detector. The complete experimental procedure is presented. In absence of candidates, updated estimates of the flux upper limits both for the CR-39 “stand alone” detector and for the global MACRO detector are presented for magnetic monopoles, nuclearites and charged Q-balls.     

Reactor antineutrino background at Gran Sasso

Summary In a recent paper, I have pointed out an important source of background for the detectors of low-energy (<10 MeV) electronic antineutrinos:the nuclear power stations. In this paper, I give more details on this background and its consequences at the location of the Gran Sasso laboratory which will become soon the largest underground centre in the world.

---

Riassunto In un recente lavoro si è evidenziata un'importante sorgente di background per i rivelatori degli antineutrini elettronici a bassa energia (<10 MeV): le centrali nucleari. In questo lavoro si danno ulteriori dettagli su questo background e le sue conseguenze sull'ubicazione del laboratorio del Gran Sasso che diventerà presto il piú grande laboratorio sotterraneo nel mondo.

---

Резюме В этой работе указывается важный источник фона для детекторов низкоэнергетических (<10 МэВ) электронных антинейтрино: атомные электростанции. Провосится оценка этого фона и его следствия в месте расположения лаборатории Гран Сассо, которая вскоре станет крупнейшим подземным исследовательским центром.

     

The LVD experiment at Gran Sasso

Summary The Large-Volume Detector (LVD) in the Gran Sasso underground Laboratory is a multipurpose detector consisting of a large volume of liquid scintillator (at present 562 tons are in data taking) interleaved with limited-streamer tubes. Several physical problems are investigated with LVD, the major being the search for neutrino bursts from gravitational stellar collapses in our Galaxy. In this paper we discuss some results on cosmic neutrinos and cosmic-ray muons obtained with the first of the five towers of LVD (operational since June 1992) and part of the second tower (operational since June 1994). The results of the search for supernovae neutrinos show that LVD is a neutrino observatory able to detect neutrinos of different flavours from gravitational stellar collapses in all our Galaxy, over a wide range of burst durations. Indeed, the carbon-based liquid-scintillator target gives a unique possibility to directly detect neutral- and charged-currents neutrino interactions with a very good signature. This characteristic of LVD allows us to make an indirect estimate of the neutrino rest mass and of neutrino oscillations from supernovae in our Galaxy. No evidence for burst candidates has been found in the data recorded from June 1992 to March 1995, for a total live time of 682 days and a total exposure of 613 tons per year. We present the results of a time coincidence analysis between low-energy signals, eventually due to neutrinos of different flavours, and γ-ray bursts (GRBs) detected by the BATSE experiment. This search covers the period from June 1993 to March 1995, during which 41 GRBs have been selected from the BATSE data. Since no excess of events in LVD has been found, upper limits on the neutrino fluxes are reported for (ν_e, p), and for neutral- and charged-currents neutrino interactions of different flavours with the C-nuclei of the scintillator. The muon intensity as a function of slant depth is presented. These measurements, obtained during a live time period of 11.556 hours, cover a slant depths range from about 3000 to about 20 000 hg/cm² of standard rock and extend over five decades of intensity. An interesting result is that the muon flux is independent of slant depth beyond a depth of about 14 000 hg/cm² of standard rock, and corresponds to near horizontal muons. This is direct evidence that this flux is due to atmospheric neutrinos interacting in the rock surrounding LVD.     

The EAS-TOP detector at Gran Sasso

Summary EAS-TOP is a detector of the extensive air showers that very high-energy cosmic rays (E ₀≥10¹⁴eV) produce in the atmosphere. The array is located on top of the underground Gran Sasso Laboratory in central Italy; a subarray (11 modules of the e.m. detector) has been operating since the end of 1987. From such data the stability of the detector, and the accuracies in the determination of the arrival directions and in the reconstruction of the electron lateral distribution and of the shower size are derived. The results obtained on VHE-UHE γ-ray sources in the first months of operation are presented. To speed up publication, the proofs were not sent to the authors and were supervised by the Scientific Committee.     

Search for WIMPs with enriched xenon at Gran Sasso

Summary A low-activity liquid-xenon scintillator is running at the Gran Sasso National Laboratory of INFN using liquid Kr-free xenon enriched at 99.5% in¹²⁹Xe. The result of adark matter direct search—looking also for the annual modulation effect—is presented. Preliminary exclusion plots both for coherent and spin-dependent coupled WIMPs are evaluated. The authors of this paper have agreed to not receive the proofs for correction.     

Results from DAMA/LIBRA at Gran Sasso

The DAMA project is an observatory for rare processes and it is operative deep underground at the Gran Sasso National Laboratory of the I.N.F.N. In particular, the DAMA/LIBRA (Large sodium Iodide Bulk for RAre processes) set-up consists of highly radiopure NaI(Tl) detectors for a total sensitive exposed mass of ?250 kg. Recent results, obtained by this set-up by exploiting the model independent annual modulation signature of Dark Matter (DM) particles, have confirmed and improved those obtained by the former DAMA/NaI experiment. A model independent evidence for the presence of Dark Matter particles in the galactic halo is cumulatively obtained at 8.2?σ C.L. No systematics or side reactions able to account for the measured modulation amplitude and to contemporaneously satisfy all the many specific requirements of the signature have been found or suggested by anyone over more than a decade. An example of one of the many possible model dependent corollary quests for the candidate particles and for the related astrophysical, nuclear and particle physics scenarios is presented considering the whole cumulative exposure. Future perspectives are shortly addressed.     

Search for electron antineutrino interactions with the Borexino Counting Test Facility at Gran Sasso

Electron antineutrino interactions above the inverse beta decay energy of protons (E_ν̄e>1.8 MeV) were looked for with the Borexino counting test facility (CTF). One candidate event survived after rejection of background, which included muon-induced neutrons and random coincidences. An upper limit on the solar ν̄_e flux, assumed having the ⁸B solar neutrino energy spectrum, of 1.1×10⁵ cm^-2 s^-1 (90% C.L.) was set with a 7.8 ton × year exposure. This upper limit corresponds to a solar neutrino transition probability, ν_e→ν̄_e, of 0.02 (90% C.L.). Predictions for antineutrino detection with Borexino, including geoneutrinos, are discussed on the basis of background measurements performed with the CTF. PACS 13.15.+g, 14.60.St, 13.40.Em, 96.60.Hv, 96.60.qd, 23.40.Bw     

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

The present study is based on the sample of 2.9×10⁶ single muons observed by the Large Volume Detector (LVD) at the underground Gran Sasso Laboratory during 36 500 live hours from June 1992 to February 1998. We have measured the muon intensity at slant depths from 3 to 20 km w.e. Most events are high-energy downward muons produced by meson decay in the atmosphere. The analysis of these muons has revealed the power index γ of the π and K spectrum: γ=2.76±0.05. The remainders are horizontal muons produced by the neutrino interactions in the rock surrounding the LVD. The value of this flux near 90° is (6.1±2.7)×10⁻¹³ cm⁻² s⁻¹ sr⁻¹. The results are compared with the Monte Carlo simulations and the world data. From Yadernaya Fizika, Vol. 66, No. 1, 2003, pp. 125–132. Original English Text Copyright ? 2003 by Aglietta, Alyea, Antonioli, Badino, Bari, Basile, Berezinsky, Bersani, Bertaina, Bertoni, Bruni, Cara Romeo, Castagnoli, Castellina, Chiavassa, Chinellato, Cifarelli, Cindolo, Contin, Dadykin, Dos Santos, Enikeev, Fulgione, Galeotti, Ghia, Giusti, Gomez, Granella, Grianti, Gurentsov, Iacobucci, Inoue, Kemp, Khalchukov, Korolkova, P. Korchaguin, V. Korchaguin, Kudryavtsev, Luvisetto, Malguin, Massam, Mengotti Silva, Morello, Nania, Navarra, Periale, Pesci, Picchi, Pless, Ryazhskaya, Saavedra, Saitoh, Sartorelli, Selvi, Taborgna, Talochkin, Trinchero, Tsuji, Turtelli, Vallania, Vernetto, Vigorito, Votano, Wada, Weinstein,Widgoff, Yakushev, Yamamoto, Zatsepin, Zichichi. The authors represent the LVD Collaboration This article was submitted by the authors in English.     

First results from the XENON10 dark matter experiment at the Gran Sasso National Laboratory

The XENON10 experiment at the Gran Sasso National Laboratory uses a 15 kg xenon dual phase time projection chamber to search for dark matter weakly interacting massive particles (WIMPs). The detector measures simultaneously the scintillation and the ionization produced by radiation in pure liquid xenon to discriminate signal from background down to 4.5 keV nuclear-recoil energy. A blind analysis of 58.6 live days of data, acquired between October 6, 2006, and February 14, 2007, and using a fiducial mass of 5.4 kg, excludes previously unexplored parameter space, setting a new 90% C.L. upper limit for the WIMP-nucleon spin-independent cross section of 8.8x10(-44) cm2 for a WIMP mass of 100 GeV/c2, and 4.5x10(-44) cm2 for a WIMP mass of 30 GeV/c2. This result further constrains predictions of supersymmetric models.     

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

Summary We 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.

---

Riassunto Si descrive l'esperimento LVD (Large Volume Detector) del laboratorio del Gran Sasso, che rappresenta il naturale sviluppo dell'esperimento 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, l'esperimento LVD è a multiscopi ma con diverse priorità delle ricerche. L'obiettivo principale è l'astronomia neutrinica, in primo luogo la rivelazione di neutrini da collassi gravitazionali stellari, e poi neutrini di alta energia e neutrini solari. Dato l'alto numero previsto di interazioni di neutrini (∼900 per un collasso alla distanza del centro galattico) da stelle collassanti, l'esperimento LVD costituisce, a differenza degli attuali esperimenti, un vero e proprio osservatorio neutrinico, in grado di compiere un'analisi dettagliata delle distribuzioni energetica e temporale del burst. Oltre all'astrofisica neutrinica, con l'esperimento LVD si possono compiere ricerche in fisica della radiazione cosmica e di particelle elementari ad altissime energie.

---

Резюме В 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.

     

High-energy cosmic-ray physics with an EAS array on the top of the Gran Sasso Laboratory

Summary An air shower array on top of the underground Gran Sasso Laboratory (GSL) can give valuable information in the field of high-energy cosmic-ray physics. We discuss the performances of a specific apparatus (EAS-TOP) operating both in coincidence with the underground array (i.e. for measuring the total primary energy of multimuon events) and as an autonomous air shower detector (for studies of ultra-high-energy gamma-ray astronomy, cosmic-ray anisotropies and primary composition).

---

Riassunto Un apparato per EAS posto in superficie nella zona sovrastante il laboratorio sotterraneo del Gran Sasso può fornire utili informazioni sulla radiazione cosmica primaria. Qui si presenta un apparato (EAS-TOP) the funzionerà sia in coincidenza con gli apparati posti nel tunnel per misure sull'energia primaria degli eventi multimuonici sia in modo autonomo come rivelatore EAS per ricerche di γ-astronomia ad energie molto elevate, di anisotropia dei raggi cosmici primari, e di composizione primaria.

---

Резюме Установка для регистрации ШАЛ над подземной лабораторией Гран Сассо может дать полезную информацию для физики космических лучей высоких энергий. Мы обсуждаем возможности установки EAS-TOP, работающей как в совпадении с подземными детекторами (для измерения полной начальной энергии в многомюинных событиях), так и в автономном режиме—для исследований в области гамма-астрономии сверхвысоких энергий, измерений анизотропии космических лучей и химического состава первичного излучения.

     

Search for supermassive magnetic monopoles with the MACRO detector at the gran sasso laboratory

We present the results of the search for supermassive magnetic monopoles with the MACRO experiment. Our detector is equipped with three independent subdetectors (liquid scintillation counters, limited streamer tubes and nuclear track detectors), operating in different ranges of monopole velocity. In several years of data taking no candidates were found; the present flux upper limits are the level of half the Parker Bound for β > 10⁻⁴; for 10⁻⁴ < β < 5 × 10⁻² the limit is the best existing.     

Measurements of the integrated muon intensity at large zenith angles

Precision measurements of the zenith-angle distributions of muons in the range 61°–89° are performed using the DECOR coordinate detector. The total number of selected events is more than 20 million. The dependence of the integrated muon intensity on the zenith angle is determined for several threshold energies in the range from 1.7 to 7.2. GeV. The experimental results in these ranges of zenith angles and threshold energies are obtained for the first time. It is demonstrated that the dependence of the integrated muon intensity on the zenith angle is adequately described by a simple analytical relationship.