Recent Results from MICE on Multiple Coulomb Scattering and Energy - - PowerPoint PPT Presentation

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Recent Results from MICE on Multiple Coulomb Scattering and Energy - - PowerPoint PPT Presentation

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Recent Results from MICE on Multiple Coulomb Scattering and Energy Loss Scott Wilbur on behalf of the MICE collaboration University of Sheffield Scott Wilbur MICE Scattering and Energy Loss 1 Ionization Cooling Emittance change depends

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SLIDE 1

Recent Results from MICE on Multiple Coulomb Scattering and Energy Loss

Scott Wilbur

  • n behalf of the MICE collaboration

University of Sheffield

Scott Wilbur MICE Scattering and Energy Loss 1

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SLIDE 2

Ionization Cooling

  • Emittance change depends on energy loss and multiple Coulomb scattering
  • Energy loss reduces momentum
  • Scattering increases entropy of the beam
  • RF re-acceleration restores pL

dǫn dz ≈ − ǫn β2

relEµ

dE dz

  • +

1 β3

rel

β⊥(13.6 MeV)2 2EµmµX0c2

  • We want to understand both energy loss and scattering terms

Scott Wilbur MICE Scattering and Energy Loss 2

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SLIDE 3

The MICE Detector

Electron Muon Ranger (EMR) Pre-shower (KL) ToF 2 Time-of-flight hodoscope 1 (ToF 0) Cherenkov counters (CKOV) ToF 1 MICE Muon Beam (MMB) Upstream spectrometer module Downstream spectrometer module Absorber/focus-coil module Liquid-hydrogen absorber Scintillating-fibre trackers Variable thickness high-Z diffuser

7th February 2015

MICE

  • TOF counters measure location and time of particle hits
  • Trackers measure trajectories and momenta

– Scattering and energy loss analyses have been done with no tracker field – Further studies are using data with tracker fields to refine measurements

  • Absorber is Lithium Hydride or liquid Hydrogen

Scott Wilbur MICE Scattering and Energy Loss 3

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SLIDE 4

Overview of Multiple Coulomb Scattering

  • The PDG recommends the formula

θ0 ≈ 13.6MeV pµβrelc

  • ∆z

X0

  • 1 + 0.038 ln

∆z X0

  • GEANT4 uses full Legendre polynomial expansion
  • Other models also considered: Moliere, Cobb-Carlisle
  • MUSCAT showed poor agreement between theory and low-Z material data
  • MICE has taken scattering data on a LiH target:

– 81% 6Li, 4% 7Li, 14% 1H (traces of C, O, Ca)

  • Results are compared to multiple theories and models

Scott Wilbur MICE Scattering and Energy Loss 4

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SLIDE 5

Scattering Data

Field-off data sets from ISIS run periods 2015/03 and 2015/04

  • Measure scattering with empty channel
  • Prediction: convolve with physics model of scattering
  • Measure scattering with absorber
  • Deconvolve measured distribution
  • χ2 comparison between data and prediction
  • Calculate width of scattering distribution: Θ(p)

Scott Wilbur MICE Scattering and Energy Loss 5

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SLIDE 6

Selection

  • Require one upstream track and at most one downstream track

(if no DS track, set scattering angle to overflow value)

  • TOF cut to select muons at a target momentum
  • Require US track to extrapolate to within DS tracker even if it scatters 12 mrad
  • utward

Scott Wilbur MICE Scattering and Energy Loss 6

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SLIDE 7

Scattering Data

Define projection angles: θy = atan pDS · (ˆ y × pUS) |ˆ y × pUS||pDS|

  • θx = atan

pDS · (pUS × (ˆ y × pUS)) |pUS × (ˆ y × pUS)||pDS|

  • so that θ2

x + θ2 y ≈ θ2 scatt and:

cos(θscatt) = pUS · pDS |pUS||pDS|

Scott Wilbur MICE Scattering and Energy Loss 7

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SLIDE 8

Tracker Acceptance

  • Match upstream and downstream track
  • TOF selection
  • Calculate scattering angles θx and θy
  • Define downstream acceptance:

reconstructed tracks in MC truth θ bin tracks in MC truth θ bin

_x (mrad) 0.06 0.04 0.02 0.02 0.04 0.06 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

MICE preliminary [simulation]

ISIS Cycle 2015/04

_y (mrad) 0.06 0.04 0.02 0.02 0.04 0.06 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

MICE preliminary [simulation]

ISIS Cycle 2015/04

Tracker Acceptance Tracker Acceptance

Scott Wilbur MICE Scattering and Energy Loss 8

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SLIDE 9

Deconvolution

  • Deconvolve observed scattering distribution to remove effects of detector resolution,

etc

  • Use an iterative algorithm that uses the conditional probability of a true scattering

angle given an observed scattering angle P(Ci|Ej) = P(Ej|Ci)P0(Ci) Σnc

l=1P(Ej|Cl)P0(Cl)

  • We measure Ej = ∆θtracker

y

, the measured deflection angle in the first tracker plane

  • We want to know Ci = ∆θabs

y

, the deflection angle in the absorber

Scott Wilbur MICE Scattering and Energy Loss 9

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SLIDE 10

Scattering Results

(radians)

X

θ ∆ 0.06 − 0.04 − 0.02 − 0.02 0.04 0.06 Probability per mrad

3 −

10

2 −

10

MICE Preliminary ISIS cycle 2015/04

LiH, Muon Beams, MAUS v2.9.1

MICE Preliminary

LiH, Muon Beams, MAUS v2.9.1 172 MeV/c 200 MeV/c 240 MeV/c

(radians)

Y

θ ∆ 0.06 − 0.04 − 0.02 − 0.02 0.04 0.06 Probability per mrad

2 −

10

MICE Preliminary ISIS cycle 2015/04

LiH, Muon Beams, MAUS v2.9.1

MICE Preliminary

LiH, Muon Beams, MAUS v2.9.1 172 MeV/c 200 MeV/c 240 MeV/c

  • θx and θy measured at each momentum point using deconvolution
  • Final value is Θ = width of gaussian fit from +40 to −40 mrad

Scott Wilbur MICE Scattering and Energy Loss 10

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SLIDE 11

Θ as a Function of Momentum

  • Scan across momentum range and measure Θx and Θy in each bin
  • Compare to PDG formula with fit for a =
  • z

X0 (1 + 0.038 ln z X0 )

Momentum (MeV/c) 160 180 200 220 240 (milliradians)

X

̀ 12 14 16 18 20 22 24 26 28

Data 2.39) ± (a=195.39 ̀ p 13.6 a Fit to Fit plus/minus error

MICE Preliminary

ISIS Cycle 2015/04

Momentum (MeV/c) 160 180 200 220 240 (milliradians)

Y

̀ 12 14 16 18 20 22 24 26 28

Data 2.34) ± (a=191.19 ̀ p 13.6 a Fit to Fit plus/minus error

MICE Preliminary

ISIS Cycle 2015/04

  • Preliminary analysis shows that scattering is higher than predicted by GEANT

and lower than predicted by the PDG model

Scott Wilbur MICE Scattering and Energy Loss 11

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SLIDE 12

Overview of Energy Loss

  • The Bethe-Bloch formula gives

− dE dx

  • =

4π mec2 · nz2 β2 · e2 4πǫ0 2 ln 2mec2β2 I · (1 − β2)

  • − β2
  • GEANT includes Bethe-Bloch and corrections, but MICE is firmly in Bethe-Bloch

energy range

Scott Wilbur MICE Scattering and Energy Loss 12

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SLIDE 13

Energy Loss Measurement Using TOF

Electron Muon Ranger (EMR) Pre-shower (KL) ToF 2 Time-of-flight hodoscope 1 (ToF 0) Cherenkov counters (CKOV) ToF 1 MICE Muon Beam (MMB) Upstream spectrometer module Downstream spectrometer module Absorber/focus-coil module Liquid-hydrogen absorber Scintillating-fibre trackers Variable thickness high-Z diffuser

7th February 2015

MICE

  • Assume energy loss in TOF and tracker is known
  • tTOF1 − tTOF0 gives initial velocity
  • Assume energy loss in TOF1 and US tracker to find vua = velocity before absorber
  • Guess vad = velocity after absorber, assume energy loss in DS tracker
  • With known velocity at every point between TOF1 and TOF2, calculate tTOF2
  • Refine guess of vad until tTOF2 time matches observed value

Scott Wilbur MICE Scattering and Energy Loss 13

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SLIDE 14

Energy Loss Results using TOF

MPV Energy Loss MC Truth 9.18 ± 0.01 MeV MC Reco 9.12 ± 0.04 MeV Data Reco 9.23 ± 0.13 MeV

  • MC studies show good reconstruction of peak energy loss, but not shape
  • Good agreement between MC and data

Scott Wilbur MICE Scattering and Energy Loss 14

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SLIDE 15

Field-On Energy Loss Measurement

  • Data taken from ISIS run period 2017/02 and 2017/03
  • Require one upstream track and one downstream track
  • Require tracks to have pt/p > 0.1
  • Use two-dimensional TOF/tracker cut to select muons

Scott Wilbur MICE Scattering and Energy Loss 15

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SLIDE 16

Combining TOF and Tracker Measurements

  • Combine TOF01 and US Tracker to get US momentum
  • Use DS Tracker to measure DS momentum
  • Slightly improved US measurement, significantly improved DS measurement
  • Measure energy loss distribution with and without absorber

Scott Wilbur MICE Scattering and Energy Loss 16

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SLIDE 17

Convolution Fit

5 10 15 20 25 30 35 40 45 50 Momentum Change

1000 2000 3000 4000 5000 6000 7000 8000 9000

Empty Absorber (140 MeV/c) 20

✁

15

✁

10

✁

5

✁

5 10 15 20 Momentum Loss 200 400 600 800 1000 #

  • f Events

Empty Absorber (140 MeV/c)

  • Measure energy loss with no absorber, fit distribution to a gaussian G0(∆p)
  • Measure energy loss with absorber
  • Fit distribution to Ltrue × G0(∆p)

Ltrue is a Landau distribution of the true energy loss

Scott Wilbur MICE Scattering and Energy Loss 17

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SLIDE 18

Field-On Energy Loss Results

10 11 12 13 14 15 16 17 18 130 140 150 160 170 180 190 200 210 220 230 240 Momentum Change [MeV/c] Muon Momentum [MeV/c] Data Bethe-Bloch MC

  • Preliminary results: MC (energy loss modeled by GEANT) agrees with data
  • Also seems to agree well with Bethe-Bloch prediction
  • Systematic uncertainties are preliminary

Scott Wilbur MICE Scattering and Energy Loss 18

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SLIDE 19

Conclusions

  • MICE has measured Coulomb scattering and energy loss of muons in LiH with

140 MeV/c < p < 240 MeV/c

  • Data has been compared to simulation packages such as GEANT and other relevant

models

  • Multiple publications in the works (MCS paper forthcoming, energy loss in Rhys

Gardener’s thesis at Brunel)

  • Work is ongoing to refine measurements with field-on data and expand measure-

ments to liquid Hydrogen

Scott Wilbur MICE Scattering and Energy Loss 19