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CC Coherent and CC neutral pion production results from MINERvA Jos - - PowerPoint PPT Presentation

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1 CC Coherent and CC neutral pion production results from MINERvA Jos Palomino* On behalf of the MINER A collaboration Centro Brasileiro de Pesquisas Fsicas, Brazil *Supported by University of Pittsburgh CC Coherent and CC neutral pion

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

CC Coherent and CC neutral pion production results from MINERvA

José Palomino* On behalf of the MINERνA collaboration

Centro Brasileiro de Pesquisas Físicas, Brazil *Supported by University of Pittsburgh

1

Thursday, October 25, 12

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

Outline of Talk

  • CCπ0 inclusive and exclusive reconstruction.
  • CCπ+ coherent production.

2 A A π+

vµ µ-

W

W ν µ N* N π0 N

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

CCπ0 Event Topology

3

RES-CCπ0

Modules Strips Strips

Using vertex position given by Muon track to scan the γ s coming from π0. Neutrino Neutrino MC MC

NUCLEAR TARGET REGION ECAL HCAL NUCLEAR TARGET REGION ECAL HCAL Gamma Gamma Gamma Gamma Proton

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

4

CCπ0 reconstruction Data - MC

Event Selection for Anti neutrino interactions: 1 muon track with Minos Match( select anti-muons) Hits to be reconstructed, must be inside 25ns respect to Vertex time. Muon vertex must be inside fiducial volume. Showers must be reconstructed by Hough Transform ( Energetic showers ) or Angle Scan ( low energy showers ) 2 EM showers ( shower vertex should be not close to muon vertex ) Energy in Nuclear Target Region < 20 MeV

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

5 To reconstruct CCPi0 inclusive events, we will select events in certain mass range (70 - 200 MeV/c2). Cuts: 1 muon track + 2 EM showers + Energy in Target Region< 20 MeV

m"2E E (1!cos ).

Invariant Mass

Background events could be Pion charge exchange in detector and wrong reconstruction.

CCπ0 inclusive Purity (54%) Efficiency (4.2%)

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

6 Vertex Activity: Energy contained inside R = 90mm To reconstruct CCPi0 exclusive events, first we need to reduce all background events, we are using “Vertex Energy”

To choose vertex energy cut, the purity must be at least 30%

Vertex Energy

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

7 Reconstructed info: Mass = 139.47 MeV/c^2 Gamma Energy 1 = 132.05 MeV Gamma Energy 2 = 127.40 MeV Energy contained inside R = 90mm Vertex Activity = 128.37 MeV

CCπ0 reconstruction

Neutrino Data

NUCLEAR TARGET REGION ECAL HCAL

R

Gamma1 Gamma2 Muon

meaning “granularity”

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

8 Reconstructed info: Mass = 130.88 MeV/c^2 Gamma Energy 1 = 164.32 MeV Gamma Energy 2 = 155.12 MeV Energy contained inside R = 90mm Vertex Activity = 0 MeV

CCπ0 reconstruction - exclusive

Neutrino Data

NUCLEAR TARGET REGION ECAL HCAL

R

Gamma1 Gamma2 Muon

Thursday, October 25, 12

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

9

CCπ0 exclusive Purity (67%) Efficiency (7%)

To reconstruct CCPi0 exclusive events, we select events with:

  • vertex energy less than 13MeV
  • mass between 40 - 240 MeV/c2.

Invariant Mass after vertex energy cut

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

10 dEdx Michel Electrons dEdx Gamma from Pi0 decay MINERvA detector allow us identify Gammas and Electrons. dEdx tool is good for pid particles on EM showers. To remove Background, we can look at dEdx to isolate gammas.

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

Kinematics Plots

11

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

12 Inclusive Events Inclusive Events Inclusive Events Inclusive Events

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

13 Exclusive Events Exclusive Events Exclusive Events Exclusive Events

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

Cross Section

14 Steps 1.- Background substraction 2.- Unfold ( bayesian ) 3.- Efficiency correction

@ @x

  • i

¼ P

j

UijðNj BjÞ niixi ;

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

15 Inclusive Events Inclusive Events Area normalized!!

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

16 Exclusive Events Exclusive Events Area normalized!!

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

17

Charged Current Coherent Pion Production

A A π+

vµ µ-

W

The defining feature of the interaction is that the hadronic final state contains a single pion and a residual nucleus is in its ground state. Coherent interactions have a great practical application to neutrino experiments because NC coherent pion production is part of the background to the ve appearance measurement. The cross sections are low and backgrounds (usually from resonance pion production processes) are large. Measurements have been made for CC, however recent measurements could not find evidence at the very lowest energies. NC coherent has only been estimated from the sum of signal plus background.

details at Aaron Higuera poster “Charged Current Charged Pion and Charged Current Coherent Pion Production”

Thursday, October 25, 12

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

18

  • /2mE

2

x = Q

0.2 0.4 0.6 0.8 1 1.2

Events / 0.05

0.2 0.4 0.6 0.8 1 1.2 1.4

3

10 ×

DATA Two tracks

2

< 0.2 (GeV/c)

2

Q

2

> 0.2 (GeV/c)

2

Q

MINERvA Prelim inary

9.43e19 POT

2

(GeV/c)

2

Q

0.2 0.4 0.6 0.8 1

2

Events / 0.025 (GeV/c)

100 200 300 400 500 600 700 800 900

DATA Two tracks

MINERvA Prelim inary

9.43e19 POT

Towards a Data-Driven Analysis

According to Partially Conserved Axial vector Current models (PCAC) CC coherent pion production must be produced at very low Q2 (Q2 <m2π ) in order to be in the PCAC regime. MINERvA will take that assumption as a start point in its effort to isolate CC coherent pion

  • production. This analysis requests two tracks coming out of a common vertex in the tracker and one
  • f them identified as a muon using MINOS near detector (MINERvA muon spectrometer).

A Q2 < 0.2 (GeV/c)2cut emphasize small x for coherent pion production, since <Eπ> for coherent is larger than <Eπ> for resonances, a x < 0.2 cut enriches the coherent sample.

Q2 = 2Eν(Eµ − Pµcosθµ) − m2

µ

Eν = Eµ + Eπ

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

19 The 4-momentum transfer to the nucleus |t| = (q-pπ)2 must be small by definition. By requiring kinematic cuts (Q2< 0.2 (GeV/ c)2 and x < 0.2 ) MINERvA is able to isolate CC Coherent candidates.

Towards a Data-Driven Analysis

Strip Number Module Ev = 6.51 GeV Eπ = 2.37 GeV Q2 = 0.038 (GeV/c)2 |t| = 0.001(GeV/c)2 x = 0.008 Data Run 2019 Subrun 5 Gate 339

x view(from above)

Charged Current Coherent Pion Production Candidate

2

(GeV/c)

2

)

  • |t| = (q-p

0.2 0.4 0.6 0.8 1

2

Events / 0.025 (GeV/c)

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

3

10 ×

DATA Two tracks & x< 0.2

2

< 0.2 (GeV/c)

2

Q

MINERvA Prelim inary

9.43e19 POT

Thursday, October 25, 12

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

Summary

20

  • MINERvA has the capability to study π0 production for

both neutrino and anti-neutrino and isolate exclusive process using energy around vertex. NCπ0 production is a large background to neutrino oscillation.

  • MINERvA is able to isolate CC Coherent Candidates.

With high statistics and good tracking capabilities MINERvA will provide a precision measurement of the coherent pion production cross section of multiple nuclear targets.

  • The algorithm to isolate, reconstruct and identify

electromagnetic showers works for π0 identification. Preliminary results are close.

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

Backup Slides

21

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Energy at the Vertex

/g)

2

Visible Energy (MeVcm

10 20 30 40 50

/g)

2

Events / (MeVcm

50 100 150 200 250 300 350 400

DATA COH QE RES W<1.4 1.4<W<2.0 <1.0

2

W>2.0 Q DIS

MINERvA Prelim inary

POT Normalized 9.43e19 POT

/g)

2

Visible Energy (MeVcm

10 20 30 40 50

/g)

2

Events / (MeVcm

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

3

10 ×

DATA COH QE RES W<1.4 1.4<W<2.0 <1.0

2

W>2.0 Q DIS

MINERvA Prelim inary

POT Normalized 9.43e19 POT

Since the 4-momentum transfer to the nucleus |t| = (q-pπ)2 must be small the energy at the vertex should be consistent with two minimum ionizing particles. Q2 > 0.2 (GeV/c)2 & x > 0.2 Q2 < 0.2 (GeV/c)2 & x < 0.2

Thursday, October 25, 12

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Shower Energy reconstruction

23

Sub-Detector Constants α 1.213 KE 2.274 KH 10.55

SubDetector Reconstructed Energy(MeV) Tracker 41.36 ECal 36.26 HCal 15.63

Calorimeter # of hits Electromagnetic 20 Hadronic 25

All hits are included to calculate calorimetric constants

electron

There are minimum requirements for events when are reconstructed

No well defined for low energy Number of hits in Calorimeter is Required

Constant for Tracker k = Incoming Energy Visual Energy

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Anchor Angle Scan vs Hough Transform

24 Vertex Anchor- Angle Scan Hough Transformation startPoint Hough Transform works better when

  • pening angle < 25 degrees

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25

EM Showers on π0 sample

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Important formulas for Pi0 reconstruction

26

Ereco = α(Etracker + kECalEEcal + kHCalEHCal) (

Reconstructed Energy for electromagnetic showers:

m"2E E (1!cos ).

Invariant mass:

pγ1.pγ2 = |pγ1||pγ2|cosθγγ

Opening angle:

  • E#E

E"

Pi0 energy:

p"p #p

  • Pi0 momentum:

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

Reconstructing Photons for π0’s “Angle Scan”

Every group (particle) inside the histogram will have a minimum angle and maximum angle Min angle Max angle Loop over hits to find those inside the “Cone Area”, this method can also work with shower gaps. Group 1 Group 2 Group 1 Group 2 Using vertex like reference point, It fills out a 1D histogram, where every entry is the angle between every hit and the vertex, weighted by its charge. Similar to Hough Transformation with r fixed. 27 MC Pi0 sample

*PE: photon electron

True Vertex

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28

Reconstructing Photons for π0’s “Hough Transform”

xcosθ + ysinθ = ρ

For each point in xy plane we can obtain a sinusoidal line (r,θ) in Hough Space First loop to remove energetic Blob Second loop to remove extra Blob

Thursday, October 25, 12

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

Neutrino Energy Reconstruction on CCπ0

29

A CCπ0 event is the form Using 4 momentum conservation:

Where, X replaces the typical lepton momentum used to derive the standard QE Neutrino energy formula.

R.H.Nelson, MiniBooNE arXiv:0909.1238v1

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CC Coherent and CC neutral pion production results from MINERvA José Palomino

MINERvA Detector

127 scintillator strips per plane. Tracker module = 2 planes ECAL module = 2 planes + 2 (2 mm thick) sheet of lead HCAL module = 1 plane + 1 (1 inch thick) sheet of steel

16.7 mm 17 mm

Triangular strip to allow charge sharing

µ-

30

MINOS Near Detector (Muon Spectrometer)

Scintillator Veto Wall

Liquid Helium

Steel Shield

Nuclear Target Region (C, Pb, Fe, H2O) Active Tracker Region Electromagnetic Calorimeter Hadronic Calorimeter

Side ECAL Side HCAL

Side ECAL Side HCAL

ν-Beam μ p

0.25t 30 tons 15 tons 0.6 tons 116 tons

8.3 tons total

5 m 2 m

2.14 m 3.45 m Elevation View

The MINERνA detector is comprised of a stack of MODULES of varying composition, with the MINOS Near Detector acting as a muon spectrometer. It is finely segmented (~32 k channels) with multiple nuclear targets (C, CH, Fe, Pb, He, H2O).

Thursday, October 25, 12