Event reconstruction and energy calibration using cosmic ... mcgrew/theses/trung...آ  Event...

download Event reconstruction and energy calibration using cosmic ... mcgrew/theses/trung...آ  Event reconstruction

of 56

  • date post

    07-Jun-2020
  • Category

    Documents

  • view

    0
  • download

    0

Embed Size (px)

Transcript of Event reconstruction and energy calibration using cosmic ... mcgrew/theses/trung...آ  Event...

  • Event reconstruction and energy calibration using

    cosmic ray muons for the T2K pizero detector

    Trung Le

    Stony Brook University

    Thesis defense, Dec. 10, 2009

  • Introduction

    • From atmospheric (Super-Kamiokande) and accelerator (K2K, MINOS)

    neutrino oscillation experiments

    � ∆m232 = 2.5 x 10 -3 eV2 and θ23 ~ 45

    0

    • From solar (Super-Kamiokande, SNO) and reactor (KamLAND) neutrino

    oscillation experiments

    � ∆m2 = 7.6 x 10-5 eV2 and θ ~ 370� ∆m221 = 7.6 x 10 -5 eV2 and θ12 ~ 37

    0

    � Neutrinos are massive and there are at least 3 distinct masses

    � Large mixing angles

    • CHOOZ reactor experiment (with short baseline ~ 1 km)

    � sin22θ13 < 0.1

    2

  • 3-flavor neutrino oscillations

    • Neutrino mixing νf = U νm, with νf = (νe, νµ, ντ), νm = (ν1 ,ν2, ν3)

    • Mixing matrix: three angles and one phase

    • Oscillation probability

    • νµ � νe oscillation channel (α ≡ ∆m 2

    21/ ∆m 2

    32

  • Tokai-to-Kamioka (T2K) experiment

    TokaiTokai

    KamiokaKamioka

    JJ--PARCPARC

    4

    TokaiTokai

  • T2K physics program

    • Precision measurement of atmospheric oscillation parameters using

    νµ disappearance

    � θ23 � ≈ 1%, , ∆m 2

    32 � ≈ 2%

    • νe appearance search to measure θ13 or improve the sensitivity on

    sin22θ13 by an order of magnitude.

    From T2K letter of intent (OA = 20, 5x1021 POT):From T2K letter of intent (OA = 2 , 5x10 POT):

    5

    Reconstructed neutrino energy of expected

    signal + BG. Assuming 5 yr exposure (5×1021

    POT), ∆m232 = 0.003 eV 2, sin22θ13 = 0.1

    Off-axis angle 20 ννννµµµµ CC ννννµµµµ NC 1ππππ 0 Beam ννννe Signal ννννe

    Generated in F.V. 10713.6 4080.3 292.1 301.6

    1R e-like 14.3 247.1 68.4 203.7

    e/π0 3.5 23.0 21.9 152.2

    0.4 < Erec < 1.2 GeV 1.8 9.3 11.1 123.2

  • θ13 sensitivity (T2K official plots)

    5×1021 POT at 50 GeV, 22.5kt, δCP=0, normal hierarchy

  • T2K neutrino beamline

    1 1

    0 m

    • Off-axis neutrino beam, off-axis

    angle 2-2.5 deg., Eν ~ 0.6 GeV at

    2.5 deg.

    • The peak energy corresponds to

    the first oscillation maximum given

    the 295 km baseline and ∆m232.

    • About 0.5% of νe at peak energy

  • Neutrino beam monitor

    • Muon monitor

    � Detect µ+ from π+� µ+ νµ decay

    � Real time status monitor:

    � Proton beam position on target

    � Horn performance 10 m

    • On-axis neutrino detector

    � Monitor ν beam direction and profile on a day-by-day basis.

    � Measure ν beam direction within 1 mrad. accuracy.

    8

    (INGRID)

    10 m

  • Near detector at 280 m

    • Measure the properties of the neutrino beam before oscillation

    • P0D (π0 detector): � Scintillator sampling detector

    � Measure NC1π0 cross section

    • Tracker: � Two Fine-Grained Detectors + 3 Time

    Projection Chambers (TPC)

    � One FGD filled with water

    B = 0.18~ 0.2 T

    � One FGD filled with water

    � High-resolution tracking chambers with Micromegas readout

    � Measure νµ, νe spectra for ν oscillations.

    • ECAL (Electromagnetic calorimeter): � Around the tracker + downstream ECAL

    � Lead + rectangular scintillator with double- end readout.

    • SMRD (Side Muon Range Detector): � Scintillator detectors inserted in iron yokes

    of the magnet.

    � Muon range detector

    � Cosmic muon trigger + veto

  • π0 detector (P0D)

    WATER TARGET

    Scintillator sampling detector: tracking + calorimetry

    Dimensions: 2200 (X) x 2340 (Y) x 2404 (Z) mm

    Masses: 17,585 kg (full), 14,668 kg (empty)

    ECAL: Scintillator (34 mm) + Lead (5 mm)

    TARGET: Scintillator (34 mm) + water ( 30 mm)

    Total channels: 10400

    ν2.4-2.8 mm 17.0mm

    ±0.5

    10

    8.50mm

    ±0.25

    ±0.5

    16.50mm

    ±0.25

    33.0mm ±0.5

    � Since SK is a water Cherenkov detector

    � π0 production cross section on water.

    � statistical subtraction of events with

    water out from water in to determine cross

    section on water

  • Photo-sensor: Multi-Pixel Photon Counter • Array of avalanche photodiodes

    • Developed by Hamamatsu & customized for T2K

    • About 11000 MPPCs installed in the P0D

    • MPPC characteristics: � Active area : 1.3 x 1.3 mm

    � Num. of pixels : 667 (50 x 50 µm2 each)

    � Operation voltage : 70 V

    � PDE at 515 nm : > 25 %

    � Dark count : < 1.35 MHz @ 25C (Gain = 7.5 x 105)� Dark count : < 1.35 MHz @ 25C (Gain = 7.5 x 105)

    � Operational in magnetic field (0.2 T) 1.3 mm

    68.5 69.0 69.5 70.0 70.5 71.0 71.5 0.0

    2.0

    4.0

    6.0

    8.0

    10.0

    12.0

    Bias Voltage / V

    G a in

    /1 0 ^5

    15℃

    20℃

    25℃

    LED amplitude spectrum

  • Event reconstruction

  • Signal and background events

    signal eventThe ππππ 0 detector is designed for:

    � Measure neutral-current single π0

    � Detect and reject charged-current ν interactions

    Reconstruction steps:

    � Separate neutrino interactions using time

    ν

    νµ + N � νµ + N + π 0

    600 MeV/c π0

    13

    background event

    170 MeV/c muon

    P0D

    P0D

    450 MeV/c π0

    � Separate neutrino interactions using time

    � Detect ν interactions (µ-)

    � Line detection in two dimensions

    � Track matching and fitting

    � Particle id (p, µ-)

    � Reconstruct neutral-current single π0

    � π0 vertex finder

    � π0 energy momentum reconstruction

    ν

    600 MeV/c π

    νµ + n � µ - + p + π0

  • Beam spill structure and electronics readout.

    4.2µs 4.2µs 4.2µs 2-3.3s 2-3.3sSpill structure

    in spill after spill inter spill

    neutrino interactions delayed signals switch to cosmic/

    TIME

    14

    neutrino interactions delayed signals switch to cosmic/ calibration mode

    Bunches

    58 ns 58 ns 58 ns

    241 ns 241 ns

    Trip-t timing structure

    Integration Reset Readout

    2.3µs

  • Charged particle track finding:

    line detection

    µ- track is relatively straight in the P0D � Line detection algorithm

    Hough transform: r = x cosθ + y sinθ, detected lines given by peak in (r,θ)

    475 MeV π0

    1500 MeV µ-

    νµ + n � µ - + p + π0

    15 Muon track detected by Hough transform

    θ

    r

    Detected 2D tracks are matched to form 3D tracks.

  • Track fitting

    �Track fitting is implemented using Kalman filter.

    �Trajectory model: straight line with random, small perturbation to particle direction (multiple scattering).

    � Extrapolation using the prediction step during the Kalman filtering.

    � Use forward-backward smoothing to obtain track parameters

    1 GeV µµµµ- MC

    16

    Deviation of reconstructed trajectory from true trajectory.

    x residual (mm)

    σσσσ ~ 2.5 mm σσσσ ~ 2.5 mm

    Gaussian fit

    1 GeV µµµµ- MC

    y residual (mm)

  • Particle identification (p, µ-)

    � Proton/muon separation

    � For low-energy heavy particle (≥ mµ), mean energy loss ~ 1/β2

    �Make a likelihood classifier using energy deposits in the 10 scintillator planes [from the stopping point]

    muon-likeproton-like

    286 MeV/c muon

    800 MeV/c proton Likelihood generated using

    17 True µµµµµµµµ-- momentum (MeV/c) True p momentum (MeV/c)

    mis-identified

    Classifier test Likelihood

  • Muon decay tagging

    Muon lifetime: 2.1µs � make delayed hits

    TIME

    CC ν interaction, µ-

    not reconstructed later bunches after-spill

    18

    Decay hits found, connected to the cluster

    ν

    �The event is tagged as charged-current interaction if ≥ 3 delayed hits are found

    �The tagging efficiency is ∼ 50%, including muon capture, for single µ- (using 15- bunch spill)

    Not decay hits since not connected to the cluster

  • Extrapolation of tracks from the TPC0 4 c m

    g a te

    µ- tracks obscured by showers or too short to be tracked by the P0D itself.

    Extrapolate using the Kalman filter: µµµµ- track reconstructed in the TPC

    P0D TPC

    TPC track

    projected track

    19

    4 c m

    g a te

    • Reverse the TPC track momentum to go

    backward, use this to project the track point to

    the P0D most downstream plane.

    • Hits within the gate are used as new position

    measurement. Measurement update the filter.

    • If the gate is empty, stop extrapolating.

    • Note: 3D extrapolation, alternate x,y

    scintillator planes.

    P0D last scintillat