Neutrino measurement with MACRO: Neutrino measurement with MACRO: neutrino oscillation, dark matter and astronomy neutrino oscillation, dark matter and astronomy studies studies Teresa Montaruli Teresa Montaruli Bari University and INFN Bari University and INFN for the MACRO Collaboration for the MACRO Collaboration Les Houches, 21 Jan.-1 Feb. 2002 School and Workshop on Neutrino Particle Astrophysics
MACRO at LNGS MACRO at LNGS MACRO at LNGS Teresa Montaruli, Les Houches, 25 Jan. 2002 2
Outline Outline Outline •Neutrino detection in MACRO since 89 to Dec. 2000 (acq end) •Through-going upward muon results: matter effects ν µ →ν →ν τ or ν µ →ν →ν sterile •Low energy topologies •Multiple scattering to infer E ν • ν astronomy results: point-like sources and diffuse flux •Search for WIMPs Clear event topologies, different energies, fully automatic analysis, no rejection of events at trigger level (efficiency, acceptance, backgrounds 76.6 × 12 × 12 m 3 can be studied using atm. muons) E th ~1 GeV Different technique than @vertical SuperKamiokande NIM A324(1993) • Min rock coverage 3150 hg/cm 2 600 ton liquid scintillator (600 ps), 20000 m 2 streamer tubes (< 1º) • Teresa Montaruli, Les Houches, 25 Jan. 2002 3
ν event topologies ν event topologies ν event topologies Throughgoing Internal Up Internal Down Throughgoing: Emedian ∼ 50 GeV 180/yr µ stop Internal Up: Emedian ∼ 3.5 GeV 50/yr Internal Down+Stopping µ : Emedian ∼ 4.2 GeV 35+35/yr (expected) Teresa Montaruli, Les Houches, 25 Jan. 2002 4
Upward throughgoing µ analysis Upward throughgoing µ analysis T.o.F. technique: Main cut: position along scint. counter from ST track in agreement inside 70 cm with that from ToF ~200 gr/cm 2 in rock absorber to reduce at 1% background from upgoing π s No scanning, fully automatic -1.25 < 1/ β < -0.75 1/ β distribution (full detector) Teresa Montaruli, Les Houches, 25 Jan. 2002 5
The backgrounds The backgrounds Incorrect β : showering events, multiple µ s; large β : µ decay First study of physical background to ν underground measurement MACRO Coll., Astr. Phys 9 (1998) Photonuclear interactions atmospheric µ ↓ produce upgoing soft particles Important for shallow detectors (Baksan, IMB while SK and Soudan2 have vetos) 243 upgoing particles between 12.2 ·10 6 µ s ↓ � ~10 -4 π/µ ↓ ~1% in throughgoing µ s ↑ ~5% in stopping µ s Teresa Montaruli, Les Houches, 25 Jan. 2002 6
Results for Upward throughgoing µ s Results for Upward throughgoing µ s Mar 89-Nov 91 (1.4y) Dec 92-Jun 93 (0.4y) Apr 94-Dec 2000 (5.5y) 26 µ↑ µ↑ 55 µ↑ µ↑ 782 µ↑ µ↑ 1/6 lower detector Lower detector Complete detector Phys. Lett. B357 (1995) 481 Phys. Lett. B434 (1998) 451 Phys. Lett. B517(2001) 59 Total n. of events 863 Backgrounds Incorrect β 22.5 Soft upgoing π 14.2 Internal ν interactions 17 Measured 809 Expected 1122 ± 17% (Bartol flux 14% checked on atmospheric µ data, cross sections (GRV94) 9%, µ energy Loss 5% (Lohmann et al.) R = 0.72 ± 0.026 stat ± 0.043 sys ± 0.12 theor Event 23 Dec 1994 Teresa Montaruli, Les Houches, 25 Jan. 2002 7
µ↑ µ↑ flux angular distribution µ↑ µ↑ flux angular distribution ∆ m 2 = 0.0025eV 2 χ 2 test on the angular distribution (10 bins) with prediction normalized to data: χ 2 /dof=25.9/9 for no-oscillations � P = 0.2% χ 2 /dof=9.6/9 for ν µ →ν τ ( ∆ m 2 = 0.0024 eV 2 sin 2 2 θ =1) � P = 37% Teresa Montaruli, Les Houches, 25 Jan. 2002 8
ν µ →ν →ν τ oscillations in upward throughgoing µ ν µ →ν →ν τ oscillations in upward throughgoing µ Peak probabilities: sin 2 2 θ =1 37% shape 66% shape × normalization ∆ m 2 = 0.0024 eV 2 Reduction factors for ν µ →ν τ MACRO threshold ~1 GeV more sensitive to vertical deficit than SK (average threshold ~6 GeV) Teresa Montaruli, Les Houches, 25 Jan. 2002 9
Angular distribution for selected sample Angular distribution for selected sample 3 box events (redundant time measurement ⇒ low background+better time resolution) same shape of full sample χ 2 /dof=9.4/7 for no-oscillations � P = 22.8% χ 2 /dof=3.7/7 for ν µ →ν τ ( ∆ m 2 = 0.0025 eV 2 sin 2 2 θ =1) � P = 81.5% Teresa Montaruli, Les Houches, 25 Jan. 2002 10
Azimuth distribution for selected sample Azimuth distribution for selected sample Full detector sample Oscillations do not affect azimuth angular distribution χ 2 /dof=2.8/11 normalizing prediction to data � P = 0.99 Teresa Montaruli, Les Houches, 25 Jan. 2002 11
Matter effects in upward throughgoing µ s Matter effects in upward throughgoing µ s When ν flavors involved in oscillations have different weak potential in matter − + ν 2 Y 4 Y n e e ± G n = × − ν ν V F B 2 Y µ , τ weak n 2 2 ν 0 sterile + for ν , - for ν n B = barion density Y n ,e = n, e/barion Matter effects can be important for ν µ →ν e , ν sterile not for ν µ → ν τ And for E ν/∆ m 2 ≥10 3 GeV/eV 2 � for HE up-throughgoing µ s For maximal mixing matter effect produces a reduction of oscillation effect � closer to predicted with no oscillations For mixing <1 enhancement for some values of parameters (MSW) Teresa Montaruli, Les Houches, 25 Jan. 2002 12
Sterile or tau ν oscillations? Sterile or tau ν oscillations? Peak probability for shape 1.8% Peak probability for shape × normalization = 8% sin 2 2 θ =1 Max mixing Vertical/horizontal more powerful test than χ 2 P. Lipari & M. Lusignoli, PRD57(1998) P best τ =8.4%/P best sterile =0.033% ⇒ 254 ν µ →ν sterile excluded at ~99% c.l. Ratio: sensitive to deviation sign, gain in statistical significance (2bins) but some feature of angular shape could be lost MACRO bin choice through simulation (MACRO Coll. Phys. Lett. B517(2001) 59) Teresa Montaruli, Les Houches, 25 Jan. 2002 13
Systematic errors in the ratio Systematic errors in the ratio •Neutrino flux sources of uncertainty: P. Lipari, Nucl. Phys. Proc Supp.91(2001) 1) K/ π fraction 2) Spectral index of CR E specrum � δ R/R ~3% •Comparison of different cross sections � δ R/R ~2% •Detector acceptance + background in MACRO events horizontal region � δ R/R ~4.6% θ Other uncertainties: seasonal variations � dR/R ~1.3% + US atmosphere profile � dR/R ≤ 1% MACRO upgoing µ s: variation in vertical/horizontal ratio R(Nov-Apr) - R(May-Oct) ≈ 0.19 ± 0.17 stat Seasonal effect difficult to calculate because neutrinos come from meson and muon decays and from all over the Earth Teresa Montaruli, Les Houches, 25 Jan. 2002 14
Internal Up events Internal Up events Selection Criteria: 1. ToF between central/top scintillator layers Vertex containment to reject up-throughgoing µ s 2. (~1% backg) DATA 161 with -1.3< 1/ β <-0.7 (eff. livetime 5.58yr) Backgrounds (wrong β , secondary hits) = 7 � 154 Uniform deficit ∆ m 2 =0.0025 eV 2 Phys. Lett. B478 (2000) 5 Teresa Montaruli, Les Houches, 25 Jan. 2002 15
Internal Down + Upward Stopping Internal Down + Upward Stopping Selection criteria: 1. no T.o.F. 2. topological cuts: fiducial volume +bottom SC layer 3. visual scanning (real+simulated events) >100 gr/cm 2 in lower detector (soft π s backg. ∼ 5%) 4. DATA: 272 events (5.6 yr), background 10 events � 262 Predictions: Φ = Φ ν ⊗ σ ν ⊗ ε(Ε µ ,θ) Uniform deficit 25% error in MC normalization 6% difference respect to MINOS Neugen • Φ ν : Bartol ν flux with geomagnetic cutoff checked on µ data (error ~ 14%) • σ ν = Q.E. + 1 π ( Lipari et al., PRL 74 (1995) 4384) + DIS (GRV-LO-94 PDF) (error ~ 15%) • ε (E µ , θ zenith ): detector response +acceptance ∆ m 2 =0.0025 eV 2 (systematic error ~ 10 %) IU and ID+UGS due to CC ν µ, NC and ν e (~13% IU and 10% UGS+ID) Phys. Lett. B478 (2000) 5 Teresa Montaruli, Les Houches, 25 Jan. 2002 16
Low energy results Low energy results Internal Upward going µ ’s • Zenith angular distributions constant deficit 154 ± 12 stat DATA: 285 ± 28 sys ± 57 theo MC: • R IU and R ID+UGS not same MC ( ∆ m 2 =0.0025 eV 2 ) : 168 ± 17 sys ± 34 theo reduction Internal down + Upgoing stopping µ ’s deficit not due to 262 ± 16 stat DATA: theor. overestimate of ν 376 ± 38 sys ± 76 theo MC: flux/cross sections MC ( ∆ m 2 =0.0025 eV 2 ) : 284 ± 28 sys ± 57 theo Data IU and ID+UGS have = ± ± ± 0 . 54 0 . 04 0 . 05 0 . 11 stat sys th MC <E ν > ~ 4 GeV ( IU ) Data = ± ± ± 0 . 70 0 . 04 0 . 07 0 . 14 stat sys th MC + ( ID UGS ) Teresa Montaruli, Les Houches, 25 Jan. 2002 17
Double Ratio Double Ratio Expected reductions for ∆ m 2 ~1-10 × 10 -3 eV 2 sin 2 2 θ= R = θ=1 Internal + Upgoing 1/2 for IU 1/4 for ID+UGS Downgoing Stop (ID not reduced) • Most of the theor. err. cancel (<5%) • Systematic err. reduced (~6%) Data: R = 0.59 ± 0.06 stat Expected (No oscillations): R = 0.76 ± 0.04 sys ± 0.04 th Expected ν µ � ν τ oscillations: R = 0.59 ± 0.04 sys ± 0.03 th (max mixing and ∆ m 2 = 2.5 x 10 -3 eV 2 ) Probability to obtain double ratio so far from expected is ~2% (including non-gaussian shape of the uncertainty of the ratio) Teresa Montaruli, Les Houches, 25 Jan. 2002 18
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