[PPT] - production in MINERA A Single 0 production in MINER using Medium PowerPoint Presentation

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Single π Single π0

0 production in MINER

production in MINERνA νA using Medium Energy beam using Medium Energy beam

(A first approach on energy resolution) (A first approach on energy resolution)

New Perspectives New Perspectives Fermilab – June 5, 2017 Fermilab – June 5, 2017

Gonzalo Díaz University of Rochester

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Wh y s t u d y n e u t r i n

π

Wh y s t u d y n e u t r i n

π

p r

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n

? p r

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u c t i

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?

Neutrino-nucleus cross sections in the range of 1-20 GeV are important for experiments like NOνA and DUNE since they need an understanding of neutrino interactions for their

scillation measurements.

Neutrino-induced π0 production processes that are background for oscillations:

Neutral-current π0 can mimic a final state electron/positron in (anti)neutrino

electron appearance.

Charged-current π0 and absorption in the nucleus can mimic quasi-elastic signal.

Charged-current single π0 production in nuclei is modeled as a decay of nucleon excitations, as well as other processes like charge exchange. Final state interactions and nuclear structure models are important to understand single π0 production inside the nucleus. More data means more tools to test these models.

T2K simulation of NC π0 background

K. Mahn – Fermilab JTEP – July 2015

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CC1π0 differential cross section as function of π0 momentum

T. Le, et al. (MINERνA collaboration), Phys. Lett. B. 749 (2015) 130-136

R e s u l t s

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π

R e s u l t s

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π

p r

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p r

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Measurements of π0 production by neutrinos have been done since mid-80s, in deuterium bubble chambers for energies up to 3 GeV. MiniBooNE published differential cross sections in mineral oil (CH2) target for lower energies, up to 1 GeV. Complementary measurements were done by SciBooNE using plastic scintillator (CH).

Neutrino-induced π0 production in deuterium

T. Kitagaki, et al., Phys. Rev. D. 34 (1986) 2554

MINERνA has recently published results of charged-current 1π0 production, using antineutrino beam of 3.6 GeV and a plastic scintillator target. Next step includes measuring 1π0 production at higher energies in heavy targets like iron and lead. Goal is to calculate both differential and absolute cross sections.

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N e u t r i n

C

C 1 N e u t r i n

C

C 1 π π p r

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u c t i

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s t u d i e s : p r

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u c t i

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s t u d i e s : s i g n a l d e fj n i t i

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s i g n a l d e fj n i t i

n

Signal is defined as:

Final state including a muon and only one π0

produced inside the nucleus either way:

➔

Directly from the neutrino interaction

➔

Through π± charge exchange process

No other mesons allowed in the final state, but

there’s no restriction for baryons. Same signal used by MINERνA before, but with a slight change. I’m using NuMI neutrino beam with energy of 6 GeV (“medium energy” configuration), as opposed to the “low energy” antineutrino beam used before. More beam energy means more intensity, and studying neutrinos allows cross section comparisons with antineutrino results.

No other mesons allowed, but it can contain any baryons Negative muon in the final state One and only one π0

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N e u t r i n

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C 1 N e u t r i n

C

C 1 π π p r

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s t u d i e s : p r

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s t u d i e s : e v e n t t

p
l
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y e v e n t t

p
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y

In contrast to MINERνA’s previous CC1π0 cross section results in plastic scintillator, this time neutrinos are required to interact with heavy nuclei targets, specifically targets 4 (only Pb) and 5 (Pb and Fe). A signal event is characterized by a long noticeable μ- track going out from the interaction vertex. Due to the its short lifetime (~10-16 s), the π0 quickly decays into two photons that have no visible track but convert into electron-positron pairs, which leave energy depositions on the active material in the form of hits.

π0 produced in the tracker (plastic scint.)

The motivation lies in looking at the event rate as well as the energy response in regions where there’s a strong presence of passive material.

π0 produced in target 4 (Pb)

Nuclear targets Tracker ECAL HCAL Nuclear targets Tracker ECAL HCAL ν beam ν beam

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P h

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r e c

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s t r u c t i

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: P h

t
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: ConeBlobs ConeBlobs

Inside the detector, hits are grouped in clusters. But clusters can be due to either, π0 decay or any other nearby activity. The challenge of reconstructing real π0→γγ events lies in the correct identification of electron-positron clusters coming from the daugher photons. The algorithm in charge of photon reconstruction is called ConeBlobs, using an angle scan selection:

It gets an angular distribution of clusters around the

vertex and selects those under the peaks.

For each of cluster selected, it looks for those

separated no more than 1 cm in adjacent planes.

Clusters that satisfy these conditions are stored in an
bject named blob.

For each angle scan, ConeBlobs stores only 2 blobs, which are the two photon candidates coming from the decay π0→γγ. Photon with larger energy is called leading; and the other one, secondary. 2 photon candidates result from ConeBlobs μ- track Interaction vertex Other activity around the vertex

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B l

b

e ffjc i e n c y a n d p u r i t y B l

b

e ffjc i e n c y a n d p u r i t y

Photon reconstruction can identify non-π0 clusters as candidates, or neglect real π0 clusters. One way to verify the quality of the is looking into the blob efficiency and blob purity. I simulated neutrino interactions in the MINERνA detector, selected signal events, and subjected them to reconstruction with ConeBlobs. Neutrino Muon Interaction vertex True photon blobs Reconstructed photon blobs

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B l

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e ffjc i e n c y a n d p u r i t y B l

b

e ffjc i e n c y a n d p u r i t y

Photon reconstruction can identify non-π0 clusters as candidates, or neglect real π0 clusters. One way to verify the quality of the is looking into the blob efficiency and blob purity. I simulated neutrino interactions in the MINERνA detector, selected signal events, and subjected them to reconstruction with ConeBlobs. The history of each of the hits of the photon candidates is tracked down to verify if they come from true π0→γγ decay. Neutrino Muon Interaction vertex True photon blobs Reconstructed photon blobs History of each hit of photon candidates is tracked down to look for coincidences with hits due to true π0→γγ decay

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Energy of true π0 hits inside reconstructed blobs

B l

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e ffjc i e n c y a n d p u r i t y B l

b

e ffjc i e n c y a n d p u r i t y

Photon reconstruction can identify non-π0 clusters as candidates, or neglect real π0 clusters. One way to verify the quality of the is looking into the blob efficiency and blob purity. I simulated neutrino interactions in the MINERνA detector, selected signal events, and subjected them to reconstruction with ConeBlobs. The history of each of the hits of the photon candidates is tracked down to verify if they come from true π0→γγ decay. With all the information gathered, efficiency and purity are calculated in the following way: Neutrino Muon Interaction vertex

Blob efficiency Energy of true π0 hits = Energy of true π0 hits inside reconstructed blobs Blob purity Energy of all hits inside reconstructed blobs =

True photon blobs Reconstructed photon blobs

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These are blob efficiencies and purities for simulated events with interaction vertex in the tracker, target 4 (Pb) and target 5 (Pb and Fe): Efficiency

Tracker (plastic scint.) Target 4 (Pb) Target 5 (Pb and Fe)

Purity

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Efficiency

Tracker (plastic scint.) Target 4 (Pb) Target 5 (Pb and Fe)

Purity > 70% efficiency > 70% purity These are blob efficiencies and purities for simulated events with interaction vertex in the tracker, target 4 (Pb) and target 5 (Pb and Fe):

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s e i n a c t i v e ma t e r i a l

My first step in the CC1π0 analysis in “medium energy” was to look at the π0 energy response in active material by looking at both types of low-level blob energies we have in the simulation:

Deposited energy: Fraction of true π0 energy deposited on active material in the form of hits
Readout energy: Energy obtained after the electronic readout of all hits reconstructed as π0 energy depositions

Tracker (plastic scint.) Target 4 (Pb) Target 5 (Pb and Fe)

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s e i n a c t i v e ma t e r i a l

Tracker (plastic scint.) Target 4 (Pb) Target 5 (Pb and Fe)

Bias towards readout at high energies High readout at low deposited Pretty bad reconstructed blobs?

My first step in the CC1π0 analysis in “medium energy” was to look at the π0 energy response in active material by looking at both types of low-level blob energies we have in the simulation:

Deposited energy: Fraction of true π0 energy deposited on active material in the form of hits
Readout energy: Energy obtained after the electronic readout of all hits reconstructed as π0 energy depositions

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s e i n a c t i v e ma t e r i a l ( a f t e r b l

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e ffjc i e n c y a n d p u r i t y c u t s ) ( a f t e r b l

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e ffjc i e n c y a n d p u r i t y c u t s )

Tracker (plastic scint.) Target 4 (Pb) Target 5 (Pb and Fe)

> 70% efficiency > 70% purity My first step in the CC1π0 analysis in “medium energy” was to look at the π0 energy response in active material by looking at both types of low-level blob energies we have in the simulation:

Deposited energy: Fraction of true π0 energy deposited on active material in the form of hits
Readout energy: Energy obtained after the electronic readout of all hits reconstructed as π0 energy depositions

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s e i n a c t i v e ma t e r i a l ( a f t e r b l

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e ffjc i e n c y a n d p u r i t y c u t s ) ( a f t e r b l

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e ffjc i e n c y a n d p u r i t y c u t s )

Tracker (plastic scint.) Target 4 (Pb) Target 5 (Pb and Fe)

Bias at high energies still there Reconstruction improves, but still a few troubles in tracker In heavy targets, it looks better

My first step in the CC1π0 analysis in “medium energy” was to look at the π0 energy response in active material by looking at both types of low-level blob energies we have in the simulation:

Deposited energy: Fraction of true π0 energy deposited on active material in the form of hits
Readout energy: Energy obtained after the electronic readout of all hits reconstructed as π0 energy depositions

> 70% efficiency > 70% purity

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Tracker (plastic scint.) Target 4 (Pb) Target 5 (Pb and Fe)

Energy resolution is defined as:

Ereco - Etrue Photon energy resolution Etrue =

where Ereco is the readout energy multiplied by calorimetric constants and Etrue is the total γ energy after the π0 decay.

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Tracker (plastic scint.) Target 4 (Pb) Target 5 (Pb and Fe)

> 70% efficiency > 70% purity Energy resolution is defined as:

Ereco - Etrue Photon energy resolution Etrue =

where Ereco is the readout energy multiplied by calorimetric constants and Etrue is the total γ energy after the π0 decay.

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Tracker (plastic scint.) Target 4 (Pb) Target 5 (Pb and Fe)

Energy resolution is defined as:

Ereco - Etrue Photon energy resolution Etrue =

where Ereco is the readout energy multiplied by calorimetric constants and Etrue is the total γ energy after the π0 decay.

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e ffjc i e n c y a n d p u r i t y c u t s )

Tracker (plastic scint.) Target 4 (Pb) Target 5 (Pb and Fe)

> 70% efficiency > 70% purity Energy resolution is defined as:

Ereco - Etrue Photon energy resolution Etrue =

where Ereco is the readout energy multiplied by calorimetric constants and Etrue is the total γ energy after the π0 decay.

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Blob efficiency and purity of π0 events from the tracker region look reasonable.

However, efficiency in targets 4 and 5 don’t. I have two hypotheses:

➔

Photons convert and deposit energy mostly inside target 4 (full Pb) whose thickness is about 1 interaction length.

➔

Photons can’t deposit energy in active material downstream target 4 since target 5 (Pb and Fe) absorbs most of that energy.

As a consequence of the last point, energy resolution of secondary photon of

target 4 and 5, especially the former one, looks bad.

The bias towards π0 readout energy respect to true deposited energy needs more understanding.
The goal of this study was to show the current low-level characterization of 1π0 events using a “medium energy” beam. The first steps

were fine, but it still needs improvements for future goals towards a precise measurement of A-dependent neutrino cross sections. Energy of true π0 hits inside reconstructed blobs Blob efficiency Energy of true π0 hits

=

Energy of true π0 hits inside reconstructed blobs Blob purity Energy of all hits inside reconstructed blobs

=

T h a n k y

u

! T h a n k y

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!

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Backup slides Backup slides

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Tracker (plastic scint.) Target 4 (Pb) Target 5 (Pb and Fe)

This is the ratio between the deposited photon energy in active material and the true photon energy.

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Tracker (plastic scint.) Target 4 (Pb) Target 5 (Pb and Fe)

This is the ratio between the deposited photon energy in active material and the true photon energy.

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Tracker (plastic scint.) Target 4 (Pb) Target 5 (Pb and Fe)

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s e i n a c t i v e ma t e r i a l ( a f t e r e ffjc i e n c y a n d p u r i t y c u t s ) ( a f t e r e ffjc i e n c y a n d p u r i t y c u t s )

Tracker (plastic scint.) Target 5 (Pb and Fe) Target 4 (Pb)

> 70% efficiency > 70% purity

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True energy: Photon energy after π0 decay.
Reco energy: Photon energy obtained from readout after applying calorimetry.

Tracker (plastic scint.) Target 4 (Pb) Target 5 (Pb and Fe)

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e ffjc i e n c y a n d p u r i t y c u t s )

True energy: Photon energy after π0 decay.
Reco energy: Photon energy obtained from readout after applying calorimetry.

Tracker (plastic scint.) Target 4 (Pb) Target 5 (Pb and Fe)

> 70% efficiency > 70% purity

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True energy: Photon energy after π0 decay.
Reco energy: Photon energy obtained from readout after applying calorimetry.

Tracker (plastic scint.) Target 4 (Pb) Target 5 (Pb and Fe)

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e ffjc i e n c y a n d p u r i t y c u t s )

True energy: Photon energy after π0 decay.
Reco energy: Photon energy obtained from readout after applying calorimetry.

Tracker (plastic scint.) Target 4 (Pb) Target 5 (Pb and Fe)

> 70% efficiency > 70% purity