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NURT-2006 Havane ,Cuba,3-7th April 2006

L3+C. Achievements of a L3-based cosmic muon telescope. Pedro Ladron de Guevara Department of Fundamental Physics. High Energy Physics Division CIEMAT-Madrid. NURT-2006 Havane ,Cuba,3-7th April 2006. LEP at CERN (Geneva)

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NURT-2006 Havane ,Cuba,3-7th April 2006

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  1. L3+C. Achievements of a L3-based cosmic muon telescope.Pedro Ladron de GuevaraDepartment of Fundamental Physics.High Energy Physics DivisionCIEMAT-Madrid NURT-2006 Havane ,Cuba,3-7th April 2006

  2. LEP at CERN (Geneva) Longitude: 6.020 E; Latitude: 46.250 N; Altitude: 450 m

  3. Introduction The succesful LEP detector L3 dedicated to the study of e+ e- collisions at CERN was equipped along 1997-98 with additional hardware and software components in order to measure the muons from cosmic radiation, using the L3 muon spectrometer. The resulting cosmic muon telescope was named “L3 + Cosmics” or “L3+C”. It worked from 1999-2000 * A setof plastic scintillators and readout system was installed on top of the magnet to provide a t0 detector. * Trigger and DAQ electronics independent of L3 to allow both experiments L3 and L3+C to run in parallel. * GPS timing. * An Air Shower Detector array of 50 scintillators covering 30 x 54 m2 was installed on top of the L3 building.

  4. L3+Cosmics EAS array * 30 m. of rockonly m * threshold ~715 GeV m spectrometer To measure: -momentum -charge -direction of the muons generated in air showers. t0 detector (202 m2 scint.) Magnet: 0.5 T ,1000 m3 Drift chambers “Trigger” and DAQ independent of L3 GPS timing (event time up to 1 ms) 1.2 x 1010 m “triggers” in 312 days of livetime

  5. Octant structure. P-chambers measure p in the plane normal to the beam :

  6. Z-chambers measure positions along the beam

  7. Schematic view of the meas. on L3+C One 3-plet at least 1 Scintillator hit Good running conditions From good quality tracks on opposite octants: -momentum resolution -max. detectable momentum -scintillator efficiencies -track selection efficiency Double octant fit Single octant fit Relative momentum resolution, versus p at detector level

  8. Physics addressed • Atmospheric muon flux and m+/m-ratio. • ap/p in primary spectrum around 1 TeV. • Solar flare of 14/July/2000. • Point source signals. • Anisotropies. • Gamma ray bursts. Search for exotic events. Primary composition in the knee region. Very forward physics. Meteorological effects of cosmic radiation. • ( blue: subjects in progress ) In this talk we will concentrate in the two first subjects

  9. The atmospheric muon flux and the m+/m- fraction

  10. The well known origin of atmospheric muon and neutrino fluxes The dominant process:

  11. Why the atmospheric muon flux is that interesting ? * Closely related to atmospheric neutrino flux * m +/ m - => constrains on cosmic primary composition. (…antimatter limits ?) * constrains for the showering models (i.e. high energy hadron nucleon cross-sections) * Directionally-related to sidereal point sources at high energies. * Sensible to middle energies solar emissions (solar flares…) when over threshold. * … muons are highly penetrant and keep track of the primary direction at high energies

  12. Atmospheric muons Current uncertainty 10 - 25 % F = F . E -g primary spectrum (from 10 GeV to 10 TeV) 0 p p,K+ X F s p+A p 10 % ( p ) 30 % ( K ) hadronic interactions (theoretical and experimental) F p,K 0 % decay (kinematics) 15 % ( m , exp.), m and n spectrum F F m n 20 - 30 % (n , theo.) Use the measured flux of muons toconstrainhadronic interactions and atmospheric neutrino flux

  13. The L3+C suroundings Simulation of the L3+C surroundings

  14. Detector and molasse simulation The muon input flux at surface, the L3+C environment and the detector response are simulated. The resulting muons are reconstructed by the same program used for the data (1.7 x 109 reconstructed Monte Carlo events) 2 x 107 data events after quality cuts for this analysis) Charge - Charge +

  15. Going from the raw data at detector level to spectrum at surface level

  16. detector level (measured) Momentum spectrum surface level (computed) Effective live time n = t . D . m Transformation matrix E . R . A migration matrix matrix of detector efficiencies function of momentum at the detector level matrix of geometrical acceptances function of the surface momentum

  17. The transformation matrix D = E.R.A R: migration matrix :The conditional probability of measuring a momentum q p i given a surface momentum q p j A: diagonal matrix of geometrical acceptance as a funcion of the surface momentum. E: diagonal matrix of detector efficiencies as a function of momentum at detector level. D ij= ei ri SMC(nselij / Ngenj)MC DW SMC : Surface area used in the MonteCarlo generator. DW : Solid angle of the zenith bin under study. ei : Includes the scintillator and trigger efficiency. ri : Selection efficiency correction. nselij : The number of selected MonteCarlo events found within a detector-level momentum bin i, wich were generated within the momentum bin j at the surface. Ngenj : Total number of MonteCarlo events generated within this surface momentum bin.

  18. Statistical and systematic uncertainties (momentum scale) Relative uncertainties of the vertical zenith angle bin measurements The individual contributions are added in quadrature.

  19. Statistical and systematic uncertainties (m flux) Relative uncertainties of the vertical zenith angle bin measurements The individual contributions are added in quadrature.

  20. Statistical and systematic uncertainties (ch. ratio) Relative uncertainties of the vertical zenith angle bin measurements The individual contributions are added in quadrature.

  21. Total uncertainty: Obtained by adding the different sources in quadrature. Muon flux uncertainty: dominated by : *The uncertainty of molasse overburden at low momenta. *The alignment and resolution uncertainty at high momenta. Minimum is 2.3 % at 150 GeV in the vertical direction. Vertical charge ratio uncertainty: Below 2 % up to 100 GeV Above 100 GeV, rises rapidily with the alignment uncertainties.

  22. Cross-check of the system

  23. Let us reconstruct , using L3+C setup (except the trigger) the L3 collisions with the same secondary topology as the cosmic muons, that is: Z => m+ m- on the Z peak.

  24. Analize the LEP events : e+ e- Z m+m-  c.m. energy : 91.27 GeV  mtrackclose to collision point  event-time in coincidence with the LEP beam crossing time pm>27.4 GeV Absolute cross-section in excellent agreement with LEP precision measurements Validates our understanding of the detector

  25. Momentum distribution of the events e+ e- Z m+m- + background The Monte Carlo events are normalized to the LEP luminosity The arrow indicates the low-momentum cut (60% of the beam energy) The events

  26. Results

  27. Measured m flux for zenith angles from 0 0 (bottom) to 58 0 (top) Inner bars :stat. uncertainty. Full bars : total uncertainty. For better visibility, an offset of 0.05 GeV2 cm-2 s-1 sr-1 was Added consecutively and lines are shown to guide the eye.

  28. Vertical m flux compared with previous results (low energy)

  29. See Ref [6] Vertical m flux compared with previous results (all energies)

  30. Measured m+/ m- charge ratio for zenith angles from 0 0 (bottom) to 58 0 (top) Inner bars :stat. uncertainty. Full bars : total uncertainty. For better visibility, an offset of 0.05 GeV2 cm-2 s-1 sr-1 was Added consecutively and lines are shown to guide the eye.

  31. Vertical m flux: * Comparison with low energy experiments gives good overall agreement above 40-50 GeV * At lower momenta a systematic slope difference seems to be present. Probably due to the systematic molasse uncertainty m+/m- ratio: *The limit is 500 GeV due to the alignment uncertainties. *In the considered range and within the experimental uncertainties, it is independent of momentum. *Mean value in vertical direction: 1.285 + - 0.003(stat.) + - 0.019 (syst.) (chi2/ndf=9.5/11.) to be compared with 1.270 + - 0.003(stat.) + - 0.015 (syst.) (average of all previous measurements) It is worth noting that the precision of the data of a single L3+C zenith angle bin is comparable to the combined uncertainty of all data collected in the past.

  32. Comparison with recent MC muon flux predictions See Ref [7]

  33. The conection of the atmospheric muon flux and neutrino flux. * m flux is a good calibration source of the atmospheric n flux * Honda (Ref [4]) has presented to the 29th ICRC,(Pune,2005) the comparison of the last measured fluxes from BESS TeV (99) BESS (2002)and L3+C with the HKKM04 model. * The ratio between measured fluxes and model show: - Agreement of < 5% in the 1-30 GeV region. - Larger disagreement out of this interval. * Honda et al. modified the DPMJET-III interaction model (differential cross sections of secondary mesons production) (only BESS data used under 50 GeV and all data for >50 GeV) * Better agreement in 1-300 GeV range obtained for m fluxes * n fluxes more reliable than that of HKKM04 in wider range.

  34. Conclusions Using the L3+Cosmics m detector (6.020E, 46.250N) we have determined: 1-the atmospheric m spectrum from 20 GeV to 3 TeV as a funtion of 8 zenith angles ranging from 00 to 600 with good overall agreement with previous data above 40-50 GeV for the vertical flux . 2- the ratio m+/m- from 20 GeV to 500 GeV for the same zenith angles as above. The mean value in the vertical direction is in perfect agreement with the average of all the previous data. 3- L3+Cosmics has extended the knowledge of the m momentum spectrum by a factor ~10 in the momentum range. 4- The precision of the data of a single L3+C zenith angle bin is comparable to the combined uncertainty of all data collected in the past. 5-The interest of L3+C data to constrain the MC p,K p-A production models and the atmospheric n flux calculations as a consequence, is pointed out.

  35. THE MOON SHADOW AND THE LIMIT OF ANTIMATTER IN THE C. R.

  36. Antiprotons in the CR Direct measurements up to 50 GeV Explained by interact. of the CR with the interstellar medium. At higher energies the detection of antiprotons should be very interesting as it should come from “exotic sources”.

  37. Indirect measurements m+/m-ratio , (model dependent) Exists a determination : (not done by L3+C) From 1530 TeV the limit ap/p  ~14 % with 67 % c.l. and big systematic uncertainties: -Primary spectrum -Hadronic interactions at HE

  38. Moon shadow CR are blocked by the Moon.  Deficit of CR when looking at the Moon (Clark,1957) Size of the deficit  effective ang. resolution. Position of the deficit  pointing error. Geomagnetic field : +ve particles deflected towards the East -ve particles towards the West  Ion spectrometer. Urban, ARTEMIS.

  39. L3+C: Good angular resolution : (0.22+- 0.04)0 for pm > 100 GeV Good pointing precision : < 0.20 Precise momentum measurement : Dpm/pm = 7% at 100 GeV Low pm,min (high rate, large deflection) Real sensitivity on the earth magnetic field. THE DEFICIT Events density vs angular distance to the Moon. a) Background from a “fake Moon” 1, hour behind its real position. b) Using the correct Moon position.

  40. Selection : Good quality events with pm > 50 GeV and angular distance to the Moon <50 Moon zenith < 600 Two energy ranges: LE (low energy) 65  100 GeV HE (High energy) > 100 Gev 6.71 x 105 selected evts What range of primary energies corresponds to 100 GeV ? From CORSIKA the peak for protons is 1 TeV And 4 TeV for He

  41. The transit of the Moon in the local system. The angular deflection due to the geom. field is a function of: -the direction of incidence -charge -momentum During a transit the deflection depends mainly on the moon position but weakly on the momentum. If we fix p=1 TeV/proton for every position of the moon we can define a coordinate system where QH: Parallel to the deflection (dispersion due to the geom. field) QV: Normal to the deflection (dispersion due to other physical effects)

  42. Shadow ( in the deflection coordinates system)

  43. Model The density in the plane around the real position of the Moon can be expressed as x0,y0 : pointing error or directional offset r = flux(ap)/(flux(p+He) ux,uy,uz define the background Nmiss : deficit f1,f2: parametrizations of the density of the shadow. • Hypothesis: • -The composition of the primaries around 1 TeV : 75 % protons, 25 % He + others • Spectral index of 2.8 similar for matter and antimatter. • Functional representation identical for protons and antiprotons.

  44. Results Angular resolution: (0.22 +- 0.04)0 Em>100 GeV (0.28+-0.08)0 65 GeV< Em < 100 GeV Pointing error < 0.20 Limit of the ap/p fraction ~1 TeV at 90 % c.l. : 11 %

  45. Outlook ALICE, the heavy ions collisions dedicated detector in LHC ( located in the same cavern and magnet than L3+C ) will implement a t0 detector based on plastic scintillators for the trigger and will use the TPC,TOF and TRD detectors to detect the atmospheric muons. (ACORDE)

  46. References [1] L3+C Collaboration. Adriani et al.,Nucl. Instrum. Methods A488 (2002) 209. [2] Measurement of the atmospheric spectrum from 20 to 3000 GeV. Phys. Letters B598 (2004) 15-32 [3] T.Hebbeker,C. Timmermans., Astropart. Phys. 18 (2002) 107. [4] T. Sanuki et al., Atmospheric neutrino and muon fluxes. 29 ICRC, Pune (2005) 00,101-104. [5] ACORDE, A Cosmic Ray Detector for ALICE. J. Arteaga et al., 29 ICRC, Pune (2005) 00,101-104 [6] Experiments providing an absolute normalization: Kiel71 : O.C. Allkofer et al., Phys. Lett. B36 (1971) 425. MARS75 : C.A. Ayre et al., J. Phys. G 1 (1975) 584. AHM79 : P.J. Green et al., Phys. Rev. D 20(1979) 1598. CAPRICE : J. Kremer et al., Phys. Rev. Lett. 83 (1999) 4241. CAPRICE : M. Bozio et al., Phys. Rev. D67 (2003) 072003. BESS : T. Sanuki et al., Phys. Lett. B541 (2002) 234. BESS : T.Sanuki et al., Phys. Lett. B581 (2004) 272, Erratum. BESS-TeV02 : S. Haino et al., astro-ph/0403704 MASS93 : M.P. De Pascuale et al., J. Geophys. Res. 98 (1993) 3501. [7] MonteCarlo models: SIBYLL2.1 : R.S. Fletcher et al., Phys. Rev. D50 (1994) 5710. BARTOL96 : Phys. Rev. D53 (1996) 1314. QGSJET01 : R. Engel et al., Proc. 26th ICRC(1999) 415. TARGET2.1 : R. Engel et al., Proc. 27th ICRC(2001) 1381. DPMJET-III : S. Roesler et al., Proc. 27th ICRC, Hamburg, 1, 439 (2001); Phys. Rev. D 57, 2889 (1998) CORT : G. Fiorentini et al., Phys. Lett. B 510 (2001) 173;hep-ph/0103322 v2 27/April/2001 HKKM04 : M. Honda et al., Phys. Rev. D70: 043008 (2004)

  47. End of presentation Thankyou !!

  48. Extra transparencies

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