Studiesof CosmogenicBackgroundto( NucleonDecayin MicroBooNE · Motivations for Nucleon Decay Everyinteractionin the SMconserves# baryonnumber. Proton#(orbound( neutron) decaycan occuronlyasa

Studies of Cosmogenic Background to Nucleon Decay in MicroBooNE

Elena Gramellini -‐‑ Yale University On behalf of the MicroBooNE collaboration

TAUP 2015 September 6-‐‑11, Torino, Italy

Motivations for Nucleon Decay

Every interaction in the SM conserves baryon number.

Proton (or bound neutron) decay can occur only as a violation of baryon number and it’s predicted by almost every GUT.

08/09/15 Elena Gramellini YaleU – TAUP 2015 2

The detection of even one nucleon decay event would be a direct evidence of physics BSM,

opening a window on GUTs exploration.

Not Only Golden Modes

… plus many others!


arXiv:1307.7335

p → e+π0 p → K+ ν

The discovery of a particular decay mode would constrain GUT models.

Need of experimental handle on many different predicted modes.

Experimental Limits on τP


1032

1033

1034

Soudan Frejus Kamiokande IMB

τ/B (years)

Super-K

p → e+ π0

p → μ+ ρ0

n → ν ω

p → e+ K 0

n → e+ K -

n → μ+ K -

p → ν K +

n → ν K 0

p → e+ K*(892)0

n → ν K*(892)0

p → ν K*(892)+

p → μ+ π0

n → μ+ π-

p → ν π+

n → ν π0

p → e+ η

p → μ+ η

n → ν η

p → e+ ρ0

n → e+ ρ-

n → ν ρ0

p → e+ ω

p → μ+ ω

n → e+ π-

n → μ+ ρ-

p → ν ρ+

p → μ+ K 0

1035

n → e- K +

Ed. Kearns

A Tool for Many Modes: LArTPC


Working principles of a Liquid Argon Time Projection Chamber: 1.  Charged particles interact in Ar

•  Produce scintillation light •  Ionize electrons

2.  Ionization e-‐‑ drift to anode 3.  Wire planes detect drift e-‐‑

Cathode plate Anode plane Electric Field

X

Y

Scintillation Light detected by PMTs

Drift Time = X position

Charge collected by wire plane

Electrons

LArTPC Key Features for Nucleon Decay


U plane induction

V plane induction

Y plane collection

⊕ ⊕ =⊕ Drift time 3D imaging Millimetric

Space Resolution

One of first MicroBooNE events

Wire pitch at the millimeter scale.

Calorimetry information

Ingredients for Nucleon Decay Detection

Lots of nucleons Lots of time

Low background [so low you need to go underground?]



Future and present LArTPCs…

X4

DUNE: Increase Nucleon Decay sensitivity in multiple channels.

40K ton active volume



X4





Study Cosmogenic Backgrounds in a LArTPC. X4


89 ton active volume


MicroBooNE and Nucleon Decay

GOAL Perform a topological search of events that mimic proton decay to estimate the mis-‐‑id

rate from cosmogenic sources.

1.  Study the decay topologies by exploiting the variety of information provided by a LArTPC.

2.  Development of a selection strategy geared towards removal of cosmogenic backgrounds for proton decay.



p → e+π0

Standard candle

p → µμ+γ High background

channel

p → K+ ν Golden channel

in LAr

Some example modes


p → e+π0 Standard candle


channel


in LAr

Some example modes




channel


in LAr

Some example modes

Elena Gramellini YaleU – TAUP 2015 15 08/09/15

Simulated Event Display for p → e+ π0

Elena Gramellini YaleU – TAUP 2015 16 08/09/15

Simulated Event Display for p → e+ π0

e

γ γ


Selection strategy

Geometry selection & PID –  π0 and e identification –  No additional vertex activity –  Proximity –  Planarity

Calorimetry selection –  Total energy deposited consistent with the proton rest mass

–  Total net momentum consistent with Fermi Momentum

e

γ γ


Selection strategy

e

γ γ





Selection strategy

e

γ γ




θ

20 08/09/15 Elena Gramellini YaleU – TAUP 2015

Selection strategy: Geometry & PID

Geometry selection & PID π0 identification e identification No additional vertex activity Proximity Planarity Calorimetry selection Total Energy deposited Total net momentum

We look for events that meet all the selection criteria: important background.



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✔ Geometry selection & PID π0 identification e identification No additional vertex activity Proximity Planarity Calorimetry selection Total Energy deposited Total net momentum





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Selection strategy: Calorimetry






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p → µμ+γ High bkg channel


in LAr

Some example modes


Simulated Event Display for p → μ+ γ


Simulated Event Display for p → μ+ γ with cosmics data overlay




µμ

γ



Selection strategy

Geometry selection & PID –  µμ/π and γ identification –  No additional vertex activity –  Proximity –  Planarity



Fiducialization γ

µμ


Selection strategy

γ

µμ Geometry selection & PID –  µμ/π and γ identification –  No additional vertex activity –  Proximity –  Planarity



Fiducialization


Selection strategy

θ

γ

µμ Geometry selection & PID –  µμ/π and γ identification –  No additional vertex activity –  Proximity –  Planarity



Fiducialization


Selection strategy: geometry

Geometry selection & PID µμ/π identification γ identification No additional vtx activity Proximity Planarity

Calorimetry selection Total energy deposited Total net momentum Fiducialization

We look for events that meet all the selection criteria:

important background.





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✖

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Selection strategy: calorimetry










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p → μ+ γ signature in 2D










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?

?



Selection strategy: fiducialization


The shower activity of the event is very close to the edge of the TPC: event rejected by planarity and fiducialization.

Selection strategy: fiducialization


The shower activity of the event is very close to the edge of the TPC: event rejected by planarity and fiducialization.


In the first MicroBooNE events, we’ve seen…

Visual summary






In the first MicroBooNE events, we’ve seen… … and more to come!

TakeawaysEven in the initial MicroBooNE cosmics data, we are

seeing for the first time topologies of interest for proton decay searches in a LAr.

This analysis is in progress.

The goal is to produce full characterization and analysis of cosmogenic backgrounds mis-‐‑ID rates.

With MicroBooNE (a 100 ton scale experiment), we can measure backgrounds, as well as develop strategies and reconstruction tools critical for future

LArTPCs proton decay searches.



Thanks for the aqention!

… if you want to hear more about MicroBooNE, don’t forget to aqend our

run coordinator‘s (Maq Toups) talk tomorrow!


ν

γ

γ γ ν

ν

ν

Back up

53

Simulated Event Display for the p → K+ν ̄

08/09/15 Elena Gramellini YaleU – TAUP 2015

Event display of a simulated p → K+ν proton decay mode.


MicroBooNE is a 170 ton LArTPC in the Booster Neutrino Beam at Fermilab.

While the mass is not sufficient to explore τP not already excluded. Surface position and currently taking cosmic

data: perfect venue to study

Cosmogenic Backgrounds in a LArTPC.

Test the potential of LArTPC in proton decay

searches.

…What About Now?

Y: 232 cm

X: 256 cm

Documents

Studiesof CosmogenicBackgroundto( NucleonDecayin MicroBooNE · Motivations for Nucleon Decay Everyinteractionin the SMconserves# baryonnumber. Proton#(orbound( neutron) decaycan occuronlyasa