Search for relativistic magnetic monopoles with the Baikal Neutrino Telescope E. Osipova -MSU (Moscow) for the Baikal Collaboration (Workshop, Uppsala,

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  • Search for relativistic magnetic monopoles with the Baikal Neutrino Telescope E. Osipova -MSU (Moscow) for the Baikal Collaboration (Workshop, Uppsala, 2006)

  • Outline:

    Introduction Detector and Site Search strategy for fast magnetic monopole Atmospheric muon simulation and suppress background events ResultsOutlook

  • IntroductionB


    P.Dirac, 1931 gg * e = n /2 hc, n=0, 1, 2..gmin = 68.5 e

    One would be surprised if nature had made no use of it P.A.M.DiracIf there is a monopole somewhere in theUniverse, even one of such object placedanywhere would be enough to explain thequantization of electric charges

  • Monopole mass and acceleration in magnetic fields of UniverseIn wide classes of models Monopole mass may be in the range 107 1014 GeVMonopole could be accelerated up to energy 1012 1015 GeV

    Monopoles with such masses may be relativistic

    In 1974 t Hooft, Polyakov independently discovered monopolesolution of the SO(3) Georgi-Glashow model Mmon ~ M V / = 1/137S.Wick, T.Kephart, T.Weiler, P.BiermanAstropart.Phys. 18(2003) 663

  • Can monopole cross the Earth?10111213141516lg( E loss, GeV)0 2 4 6 8 lg (Emon / M) Emon = 1015 Gev E mon/M < 108

    M> 107 GeV

    Monopole Energy losses, crossing the Earth on diameter1014 GeV > Mmon > 107 GeV

  • Cherenkov Light from Relativistic Magnetic Monopole

    d Nph/dl(M) = n2 (g/e)2 d Nph/dl(muon) 8300 d Nph/dl(muon) ( n =1.33)Light flux from monopole Light flux from 10 PeV muon photons /cm

  • Baikal Neutrino Telescope NT-200192 Optical modules on 8 stringsOMs are grouped in pairs ChannelTrigger >3 Chan within 500nsOM could detect fast monopole up to 100m Expected number of hits Nhit for fastMonopole vs distance from NT200 center

  • Water characteristicsAbsoptionLabs =22-24 m (480nm)ScatteringStrongly anisotropic 0.85-0.9Lscat =30-70 m

    OM response on fast monopole vs R,mp.e.R,mLscat 15m30mSeff increases by 20%p.e with delay

  • Atmospheric muon simulation The main background for fast monopole signatures are muon bundles, high energy muons and shower from muons Primary particles Air shower, muons Composition and spectral index for elements B. Wiebel-Smooth, P.Bierman, Landolt-BornststainCosmic Rays,6,1999, pp37-90CORSIKA code J.Capdevielle et. al. KfK report (1992)QGSJET1 model N.N Kalmykov Nucl.Phys. B52 (1997)Pass at depth MUM E.Bugaev Phys.Rev.D64NT200 responseto all muon energy loss processesBaikal code I.Belolaptikov will be published

  • Time distribution t = t52-t53)MCEXPt, nsMCEXPPh.el.Amplitude distribution

  • Search strategy and data analysisSelection events with high multiplicity Nhit>30To reduce the background from atmospheric muons we search for monopole from the lower hemisphere To suppress atmospheric muons a cut on time_z correlation has been applied NT-200 1000 days of live time (April 1998-February 2002)ti ,zi - time & z-coordinates of fired channels,T,Z their mean values per event t ,z - root mean square

  • Background suppression corTZ for atmospheric muon (black-EXP, red-MC) and for fast monopole from the lower hemisphere (blue)Additional cuts after reconstruction:Cut2- Nhit>35& corTZ >0 & rec. Cut3 - Nhit>Cut2& 2Cut3&>100o

    Next cuts are different for different NT200 configurationsCut5 Cut4&Rrec>10-25 m ( Rrec -distance from NT200 center)Cut6- Cut5& corTZ >0.25-0.65 No events from experimental sample pass CUTS 1-6CUT 1 : corTZ >0 & Nhit >30 leaves 0.015% of events and reduces effective area for monopole (=1) ~ 2 times

  • The main sources of background lg(Esh,TeV)Number of muons in bundle Simulated atmospheric muons satisfying CUT1 vs cascade energy (upper) and vs number of muons in bundle (lower) CUT1CUT3CUT4CUT5 MC eventsNumber of muons in bundleLg(Esh,TeVThe events with a large number ofmuons in bandle are supressed afterreconstruction with 2
  • Comparison of experimental and MC data with respect toparameters which used for background rejection for events satisfying CUT1Distance from NT200 center Reconstructed R, m, gradNumber of fired channelsSimulation describes EXP data quite well even for very rare events.MCEXPExpected from monopole

  • CUT levelPassing ratesMCEXPSeff for monopole(=1)Effective area for fast monopole (=1) decrease 2 times from CUT1 CUT6

    Passing rates versus Cut-level

  • Upper limit on the flux of fast monopoleFrom the non-observation of candidateevents in NT200 an upper limit on theflux of fast monopole is obtainedAcceptance & Upper flux limit

    Aeff Tcm2sec sr =1=0.9=0.8NT200 4.84 10163.48 10161.231016NT36+NT96 0.37 10160.25 1016 0.1 1016Upper Limit 90% C.L.(cm2sec sr)-10.46 10-160.65 10-161.8 10-16

  • NT200+=NT200 +3 external string ( 36 OMs)- Height = 210m = 200m Volume ~ 4 MtonNT200+ put into operation in 2005. The main advantage of NT200+ is the possibility to select cascades. It allows to reject background using more soft cuts. We expect increasing effective area for fast monopole at 1.5 times comparing NT200 Outlook

  • A future Gigaton Volume Detector (Baikal-GVD)Sparse instrumentation:

    90 100 strings 300 350 m lengths with 12 - 16 OM per string = 1300 - 1700 OMs (NT200 = 192 OMs) distance between strings 100 m

    Top view of the planned Baikal-GVD detector. Also shown is basic cell: a minimized NT200+ telescopeExpected sensitivity for fastmonopole (1 year GVD) Fmon < 5 10-18 cm-2 s-1 sr-1

  • CONCLUSIONBAIKAL Experimenal Upper limit on the Fast ( v/c =1) Monopole Flux (90% C.L) Fmon < 0.46 10-16 cm-2 sec-1 sr-1

    The limit on fast magnetic monopole flux obtained in this analysis is the best at the present time 2. NEW configuration NT200+ Permits to reject background using more soft cuts. Expected 1.5 times increase of effective area for fast monopole comparing NT200

    3. Gigaton Volume (km3-scale) Detector (Baikal-GVD) Expected sensitivity for fast monopole (1 year operation) Fmon < 5 10-18 cm-2 s-1 sr-1

  • Water characteristicsAbsorption and Scattering cross-section vs Strongly anisotropic 0.85-0.9

    Lscat=30-70 mLabs =22-24 m

    Absoption ScatteringOM responce vs R,mLscat 15m30mSeff increases by 20%R,mp.e. , ns, nsp.e.p.e with delay