,Ar) & (K ,Ar) Total HadronicCross Section at LArIAT · 12/07/18 Elena Gramellini -- Yale...

Lesson Learned measuring the (π- ,Ar) & (K+,Ar) Total Hadronic Cross Section at LArIAT

Elena Gramellini - Yale UniversityJuly 11th 2018

LArIAT XS analyses in 4 simple steps:

1) Select the right particle in the beamline

2) Beamline-TPC Handshake

3) Apply the “thin slice method”

4) Correct for Backgrounds and Reco effects

12/07/18 Elena Gramellini -- Yale University 2







LL: and account for the wrong ones

1) Select the right particle in beamline

12/07/18 4

LArIAT preliminaryRun II

Pos Polarity

Elena Gramellini -- Yale University

π/µ/e K p


Positive Polarity

Keep π: Mass < 350 MeV/c2

K: 350 MeV/c2 < Mass < 650 MeV/c2

1) Select the right particle in beamline

12/07/18 5


Pos Polarity

Elena Gramellini -- Yale University

π/µ/e K p


Positive Polarity

Keep π: Mass < 350 MeV/c2

K: 350 MeV/c2 < Mass < 650 MeV/c2

Indistinguishable π/µ/e

Beam Composition


Beam Composition -60A

Shower Cut for ElectronsNo Cut for Muons.

Beam Composition -100A

LL: different beam conditions mean different compositions, leading to

different bkg

Beam Composition


LL: if you can’t beat them, simulate them.

A reliable Beamline Simulation is important to to assess beamline backgrounds.

- Beam composition as a function of theincoming momentum at the TPC front face.

- Correct propagation of backgrounds in the “thinslice method” (more on this later)

2) Beamline-TPC handshake

9Elena Gramellini -- Yale University12/07/18

Beamline objects- Momentum- Projection to TPC front face

TPC objects- Multiple Tracks with associated calorimetry.

LL: radial cut!

- Reject multiple matches- Keep track of incorrect matches… they are the only one that count!!!- Know where the momentum is measured in your beamline so to

account for energy loss between beamline and TPC.

2) Beamline-TPC handshake


ELoss is the energy loss due to material upstream of the TPC (argon, steel, beamline detectors)

LL: - Minimize material in front of the TPC

- Accurate geometry survey

- Cross check of the geometry implemented in software







If you get here, you have:- A pool of beamline candidates with a measured momentum

- A track selected in the TPC that represents your incoming pion. You know where the track ends and you know the energy deposited at each point of the track.







If you get here, you have:- A pool of beamline candidates with a measured momentum

- A track selected in the TPC that represents your incoming pion. You know where the track ends and you know the energy deposited at each point of the track.

LL: do calorimetrycalibration ahead of time!

The survival probability of a particle through a thin slab of argon is:

σTot = cross section per nucleon, δX = depth of the slab,n = the density

The interaction probabilityin a thin slab is the ratio of the number of interacting particlesto the number of incident particles.

3) Thin-slice method


Since the slice is thin, we can Taylor expand and solve for the cross-section.



The game here is understanding how many pions where incident on argon at a given energy and how many interacted at that energy.

16

N Incident , N Interacting calculationInteracting

IncidentKinetic Energy (MeV)

Kinetic Energy (MeV)

We follow the TPC track slice by slice

- The slice represents the distance between each 3D point in the track

- For each slice we ask: “Is this the end of the track?”

NO: Calculate the kinetic energy at this point and fill the “incident” histogram

Elena Gramellini -- Yale University12/07/18

Beamline SelectedK+ candidate

17

N Incident , N Interacting calculationInteracting

IncidentKinetic Energy (MeV)


We follow the TPC track slice by slice

- The slice represents the distance between each 3D point in the track

- For each slice we ask: “Is this the end of the track?”

YES! Calculate the KE at this point and fill both the “interacting” and “incident” histograms



18

N Incident , N Interacting calculation



LL: Stop thinking like a neutrino physicist J0) It’s very helpful to think of the slices in terms of single

independent experiments1) One beamline candidate corresponds to several independent

“thin target experiments”.2) Long tracks populate low energy bins3) Long tracks are easier to match! The matching affects the

population of NInt and NInc Incident



19

We take the ratio of the two histograms and calculate the raw cross section

=


Raw

Cro

ss-s

ectio

n (b

arns

)


Interacting

Incident


4) Correct for Background and Reco

20

=


Interacting

Incident


We evaluate the background and the reconstruction effects on the interacting and incident distributions separately


Cro

ss-s

ectio

n (b

arns

)

Signal TopologiesσTot = σelastic + σinelastic+ σabs +

σcharge xc+ σπ-prod

22

Elastic Scattering Candidate

Absorption Candidate (π -> 3p)

Inelastic Scattering Candidate

Elena Gramellini -- Yale University 12/07/18

LArIAT Data

LArIAT Data

LArIAT Data

π Prod Candidate

LArIAT Data

Charge Exchange Candidate

LArIAT Data

Intrinsic Physics Background

23Elena Gramellini -- Yale University 12/07/18

π Decay Candidate

π Capture Candidate

π Beamline Decay (Secondaries)

LArIAT Data

LArIAT Data

LArIAT Data

+ residual electrons & muons

Beamline Background

“Intrinsic Physics” BackgroundDefinition of interaction: the tracking ends within FV.

π-Capture and π-Decay occur mainly at rest: select particles with

high incoming momentum.


Surviving Event RatioLL: cut on the incoming particle momentum so that it cannot stop inside the TPC +Start the XS from KE > 100 MeV.

Alternative approach: change signal definition, correct for background (done in kaon analysis).

“Beamline” Background

LL: Muons and electron will appear differently in NInt and NInc


“Beamline” Background


0 200 400 600 800 1000 1200 Kinetic Energy [MeV]

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

Inte

ract

ing

MC

pC

content -60ApEstimated

Muons x 2.0

Electrons x 2

Electrons x 0.5

Background Correction, Interacting


0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

Inci

dent

MC

pC

content -60ApEstimated

Muons x 2.0

Electrons x 2

Electrons x 0.5

Background Correction, Incident

+/-100% variation in electron

We know we underestimate the muons: +100% variation

XS Formula: Reconstruction Effects


Correct Interaction ID

Missed Interaction

Early Stop

Reconstructed Track

Reconstructed Track

Reconstructed Track

Great, all the slices are at the right energy!

Inefficiency in NInt @ K.E.Int

Background in NInc for K.E. < K.E.Int

Background in NInt @ K.E.Int

Inefficiency in NInc for K.E. < K.E.Int


0 200 400 600 800 1000 1200Kinetic Energy [MeV]

0

0.2

0.4

0.6

0.8

1

1.2

1.4

Int

Î Eff Correction Interacting 60A Stat Unc

Eff Correction Interacting 60A Syst Unc


0

0.2

0.4

0.6

0.8

1

1.2

1.4

Inc






0

0.2

0.4

0.6

0.8

1

1.2

1.4

Int




0

0.2

0.4

0.6

0.8

1

1.2

1.4

Inc




LL(1) Getting the correct MC truth takes more time than one would think… again, it’s the slice game!



0

0.2

0.4

0.6

0.8

1

1.2

1.4

Int




0

0.2

0.4

0.6

0.8

1

1.2

1.4

Inc




LL(2) You shouldn’t correct for interactions you’re not sensitive to: what’s the minimum angle you can see?

What angles are invisible to us?


What angles are invisible to us?



0.7

0.75

0.8

0.85

0.9

0.95

1

1.05

1.1

All

s ° 5

s

Percentage of Cross Section with Interaction Angle > 5 Deg

Backup


,Ar) & (K ,Ar) Total HadronicCross Section at LArIAT · 12/07/18 Elena Gramellini -- Yale...

Documents

Transcript of ,Ar) & (K ,Ar) Total HadronicCross Section at LArIAT · 12/07/18 Elena Gramellini -- Yale...