Detection of Cerenkov light emission in LAr

Detection of Cerenkov light emission in LAr

Ettore SegretoUniversity of L’Aquila

Ettore SegretoUniversity of L’Aquila

Cryodet International Workshop

Laboratori Nazionali del Gran Sasso 13-14 March 2006

13 March 2006 Cryodet workshop 2

OUTLINEOUTLINE Detection of visible light in coincidence with cosmic

ray muons in the ICARUS 10m3 prototype during a dedicate test run at Gran Sasso Laboratory external facility.

Geometrical features of the 3D reconstructed muons tracks.

Monte Carlo simulation of the detector and of the cosmic muon flux.

Comparison of Data with Monte Carlo results. Cerenkov radiation in a next generation large mass

LAr TPC (?)

Detection of visible light in coincidence with cosmic ray muons in the ICARUS 10m3 prototype during a dedicate test run at Gran Sasso Laboratory external facility.

Geometrical features of the 3D reconstructed muons tracks.

Monte Carlo simulation of the detector and of the cosmic muon flux.

Comparison of Data with Monte Carlo results. Cerenkov radiation in a next generation large mass

LAr TPC (?)

13 March 2006 Cryodet workshop 3Nuclear Instruments and Methods in Physics Research A 516 (2004) 348-363Nuclear Instruments and Methods in Physics Research A 516 (2004) 348-363

13 March 2006 Cryodet workshop 4

ICARUS 10m3 prototypeICARUS 10m3 prototype

The module : ~ 10m3 of LAr (14 tons). TPC (2.00m (w) x 3.26m (h) x

0.35m( l) drift length) with two read-out planes: two independent representations of the ionizing event (and possibility of 3D reconstruction).

2” quartz windowed PMT (EMI 9814BQ) -spectral sensitivity: 160 nm-600 nm- not sensitive to 128 nm LAr scintillation radiation.

128

13 March 2006 Cryodet workshop 5

Data sampleData sample The detector was exposed to cosmic ray flux at surface during a complete test

(cryogenics, electronic, acquisition system…) held in the external facility (Hall di Montaggio) of LNGS (January-May 2000).

The installation inside the 10m3 LAr volume of the EMI 9814BQ PMT was designed in order to check any possible light emission phenomena, apart from VUV scintillation emission, accompanying ionization processes.

In a limited period during the test run a sub-sample of the collected data have been acquired using the PMT signal as trigger for the detector. In principle, if no visible light emission is registered by the PMT in coincidence with the passage of particles in the liquid, no events are recorded. Indeed, we acquired a large sample of events during this dedicated test, indicating that visible light signals are associated to through-going particles.

About 1200 events produced by single penetrating muons have been selected for the present analysis

The detector was exposed to cosmic ray flux at surface during a complete test (cryogenics, electronic, acquisition system…) held in the external facility (Hall di Montaggio) of LNGS (January-May 2000).

The installation inside the 10m3 LAr volume of the EMI 9814BQ PMT was designed in order to check any possible light emission phenomena, apart from VUV scintillation emission, accompanying ionization processes.

In a limited period during the test run a sub-sample of the collected data have been acquired using the PMT signal as trigger for the detector. In principle, if no visible light emission is registered by the PMT in coincidence with the passage of particles in the liquid, no events are recorded. Indeed, we acquired a large sample of events during this dedicated test, indicating that visible light signals are associated to through-going particles.

About 1200 events produced by single penetrating muons have been selected for the present analysis

13 March 2006 Cryodet workshop 6

Events selection and reconstruction (I)Events selection and reconstruction (I)Collection view

Induction view

Typical event produced by a crossing muon in the 10m3 detector triggered with the internal PMT

Typical event produced by a crossing muon in the 10m3 detector triggered with the internal PMT

Each view of each selected event is linearly fitted to obtain the geometric parameters of the two 2D projections of

the event.

Each view of each selected event is linearly fitted to obtain the geometric parameters of the two 2D projections of

the event.

PMTPMT

13 March 2006 Cryodet workshop 7

The analytic combination of the two 2D projection of the events allows to obtain a complete 3D reconstruction of the muon track:

Entry point in the detector. Zenith (and Azimuth (angles.

The analytic combination of the two 2D projection of the events allows to obtain a complete 3D reconstruction of the muon track:

Entry point in the detector. Zenith (and Azimuth (angles.

Hall di MontaggioHall di Montaggio

Events selection and reconstruction (II)Events selection and reconstruction (II)

13 March 2006 Cryodet workshop 8

Geometrical features of selected tracks (I)Geometrical features of selected tracks (I)

The peak position in distribution means that muons propagating towards the PMT window are strongly favored, i.e. strong directionality (characteristic of Cerenkov radiation)

The left-right asymmetry (white histogram) is mainly due to the geographycal location of the detector. The presence of the Gran Sasso massif strongly suppresses the cosmic muon flux with larger values of zenith angles (>450) in the region ~ [2000,3400].

A cut was applied: only vertical muons are considered (<450) to remove asymmetry (yellow histogram). The residual asymmetry is due to the PMT position, not perfectly symmetric with resepect to the wire chamber

The peak position in distribution means that muons propagating towards the PMT window are strongly favored, i.e. strong directionality (characteristic of Cerenkov radiation)

The left-right asymmetry (white histogram) is mainly due to the geographycal location of the detector. The presence of the Gran Sasso massif strongly suppresses the cosmic muon flux with larger values of zenith angles (>450) in the region ~ [2000,3400].

A cut was applied: only vertical muons are considered (<450) to remove asymmetry (yellow histogram). The residual asymmetry is due to the PMT position, not perfectly symmetric with resepect to the wire chamber

13 March 2006 Cryodet workshop 9

Geometrical features of selected tracks (II)Geometrical features of selected tracks (II)

Most of the events are broadly distributed between 5 cm and 20 cm. The average value is < d > ≈ 10 cm. Most of the events are broadly distributed between 5 cm and 20 cm. The average value is < d > ≈ 10 cm.

Track Impact parameter w.r.t. the PMT optical window

13 March 2006 Cryodet workshop 10

Cerenkov radiation in LAr by cosmic

muons.

Cerenkov radiation in LAr by cosmic

muons.A cosmic muon (z= ±1) in ultra-relativistic regime ( 1) propagating in LAr (n 1.22) radiates visible Cerenkov photons with an angle w.r.t. its direction:

The spectrum is continuous:

Average number of Cerenkov photons detectable by the installed PMT (160nm-600nm):

A cosmic muon (z= ±1) in ultra-relativistic regime ( 1) propagating in LAr (n 1.22) radiates visible Cerenkov photons with an angle w.r.t. its direction:

The spectrum is continuous:

Average number of Cerenkov photons detectable by the installed PMT (160nm-600nm):€

cosϑ C =1

β μ nAr

⇒ ϑ C ≅ 34o

€

d2N

dν ⋅dx=

2πα

csin2 ϑ C

€

dN

dx≈ 700

photons

cm

13 March 2006 Cryodet workshop 11

Monte Carlo simulationMonte Carlo simulation Simulation code based on the GEANT 3 package. Precise description of the geometrical features and of the

materials constituting the detector. Exact spectrum (energy, azimuth and zenith angles) for cosmic

muons. Cerenkov photons production and propagation. Optical properties of the materials:

Refelectivity of the internal structures (aluminium/stainless steel). Rayleigh scattering in LAr (and no absorption).

PMT response (Quartz window transmittance and photo-cathode quantum efficiency).

Simulation code based on the GEANT 3 package. Precise description of the geometrical features and of the

materials constituting the detector. Exact spectrum (energy, azimuth and zenith angles) for cosmic

muons. Cerenkov photons production and propagation. Optical properties of the materials:

Refelectivity of the internal structures (aluminium/stainless steel). Rayleigh scattering in LAr (and no absorption).

PMT response (Quartz window transmittance and photo-cathode quantum efficiency).

13 March 2006 Cryodet workshop 12

Real data vs. MC simulationReal data vs. MC simulation

Yellow DataRed MCYellow DataRed MC

The detected light is consistent with Cerenkov radiation emission by cosmic muons.The detected light is consistent with Cerenkov radiation emission by cosmic muons.

13 March 2006 Cryodet workshop 13

From Carlo Rubbia talkFrom Carlo Rubbia talk

13 March 2006 Cryodet workshop 14

Single detector: charge imaging, scintillation, Cerenkov lightSingle detector: charge imaging, scintillation, Cerenkov light

LAr

Cathode (- HV)

E-fieldExtraction grid

Charge readout plane

UV & Cerenkov light readout PMTs

E≈ 1 kV/cm

E ≈ 3 kV/cmElectronic racks

Field shaping electrodes

GAr

13 March 2006 Cryodet workshop 15

Cerenkov photons: additional discriminationCerenkov photons: additional discrimination

+ with 500 MeV of kinetic energy

The track in the LAr TPC

Spectrum: 200nm< <600nmFull GEANT-4 simulation

Idea: use combination of charge readout and Cerenkov light to determine mass of particle (hep-ph/0402110 A. Rubbia)Idea: use combination of charge readout and Cerenkov light to determine mass of particle (hep-ph/0402110 A. Rubbia)

Drift

13 March 2006 Cryodet workshop 16

e

Signal

e

e

Background

Example: / discrimination in beta beamsExample: / discrimination in beta beams

The combination of the information from the tracking and calorimetric measurementswith the Cerenkov light provides improved particle identification. For example one can separate in this way pions from muons, a very important tool in the context of beta-beams

The combination of the information from the tracking and calorimetric measurementswith the Cerenkov light provides improved particle identification. For example one can separate in this way pions from muons, a very important tool in the context of beta-beams

20% coverage and 20% Q.E. 20% coverage and 20% Q.E.

Energy(MeV) <# > <# >

200 10168 400 16412 620

600 97284 2940 108918 3485

1000 193080 5867 204293 6244

13 March 2006 Cryodet workshop 17

ConclusionsConclusions Ionizing tracks from cosmic ray muons crossing

the ICARUS 10m3 active volume have been collected in coincidence with visible light signals from a PMT immersed in liquid argon.

By means of a detailed Monte Carlo simulation we have shown that the geometrical characteristics of the events are compatible with the hypotesys of Cerenkov light emission as the source of the PMT signals.

Ionizing tracks from cosmic ray muons crossing the ICARUS 10m3 active volume have been collected in coincidence with visible light signals from a PMT immersed in liquid argon.

By means of a detailed Monte Carlo simulation we have shown that the geometrical characteristics of the events are compatible with the hypotesys of Cerenkov light emission as the source of the PMT signals.

13 March 2006 Cryodet workshop 18

Backup Slides

13 March 2006 Cryodet workshop 19

Combinig Cerenkov and charge read-out (I)

Combinig Cerenkov and charge read-out (I)

Non destructive multiple read-out of a LAr TPC allows to reconstruct particle tracks with bubble-chamber quality. Fine granularity allows precise calorimetric measurements. Tracking and calorimetry provide momenta, particle identification,

clean e/separation …

13 March 2006 Cryodet workshop 20

Why detect Cerenkov radiation in a LAr TPC of next generation?

Why detect Cerenkov radiation in a LAr TPC of next generation?

Passive perlite insulation

≈70 m

h =20 mMax drift length

Electronic crates

A “general-purpose” detector for superbeams, beta-beams and neutrino factories with broad non-accelerator physics

program (SN , p-decay, atm , …)

A “general-purpose” detector for superbeams, beta-beams and neutrino factories with broad non-accelerator physics

program (SN , p-decay, atm , …)

13 March 2006 Cryodet workshop 21

Neutrino detection: LAr TPC vs water Cerenkov

+ n → μ − + p + n → μ − + p

€

+ X → μ − + many prongs

€

+ X → μ − + many prongs

+ n → μ − + p + n → μ − + p

K2KK2K

ICARUS 50 liters

ICARUS 50 liters

Multi prong event detection not possible with water Cerenkov

13 March 2006 Cryodet workshop 22

Pion contamination for 90% muon acceptancePion contamination for 90% muon acceptance

Kinetic energy (MeV)

Q.Efficiency = 1

Q.Efficiency = 4%

Q.Efficiency = 2%

200 0 2.07 e-14 1.93 e-08300 1.45 e-13 1.98 e-07 4.69 e-05400 1.08 e-06 2.18 e-04 2.75 e-03500 9.76 e-04 7.6 e-03 2.5 e-02600 2.21 e-02 5.38 e-02 9.61 e-02700 8.85 e-02 1.49 e-01 2.11 e-01800 2.17 e-01 2.78 e-01 3.33 e-01900 3.73 e-01 4.23 e-01 4.67 e-01

1000 4.34 e-01 4.78 e-01 5.16 e-012000 8.71 e-01 8.73 e-01 8.75 e-013000 9.53 e-01 9.53 e-01 9.52 e-01

Q.Efficiency =εcoverage ×εq.e.PMT