Rezo Shanidze

Rezo Shanidze

MC Studies in Erlangen&

Neutrinos from SN in KM3NeT ?

KM3NeT Meeting, Catania, 11-13 March, 2008

R.Shanidze, KM3NeT Meeting, Catania, 12/03/2008

MC Optimization Studies

Detection unitDetection unit. . . Detection unit

Geometry configuration

MC simulations of the different detector configurations. Comparison of the benchmark parameters: Neutrino effective area Aeff(E) Angular resolution of reconstructed : ()

PMT . . . PMT Storey

Storey . . . Storey

Different detector components and geometry configurations were considered :

OM . . . OM

• Photo-multipliers (PMT) • Optical modules (OM)

• Storey on detection

unit (string)

S. Kuch, PhD thesis, www.slac.stanford.edu/spires/find/hep/www?r=FAU-PI1-DISS-07-001


PMTs / Optical Modules/ Storeys

PMTs used in the Erlangen MC simulations: 1) Standard: 10” Hamamatsu R7081 2) Small: 3” Photonis XP53X2

OM/storey:

with large PMT a) OM with one 10” PMT b) Two OMs with 10”PMT c) ANTARES type with 3 OMs d) ANTARES type with 6 OMs with Multi-PMT OM e) Storey with 3 cylindrical OMs f) Storey with spherical OM: 36 or 42 PMTs g) Storey with spherical OM: 21 PMTs.


Geometry configurations

Basic geometry configurations: homogeneous (a), cluster (b) , ring (c,d)

a b

c d


The Reference Detector

15 x 15 strings ( 95 m)37 storey (8325 OMs) 16.5 m1 Multi-PMT OM 21x 3’’ PMT

Instrumented volume 1.05 km3

Max -track length (time) in KM3NeT ~ 2 km (7 sec)


MC Data in Erlangen

MC data produced in Erlangen (with modified ANTARES software): Gendet - GENHEN - km3 - RECO For each detector configuration, 2 x109 simulated events N CC interactions: E-1.4, 10 < E < 107 GeV, -1 <cos<1 Data sample for the reconstruction: ~ 8 x104 events / configuration

What can we study from these data samples:

- neutrino event rates ? - comparison to other experiments ? . . . What has to be studied for TDR ? . . . . .


Neutrino effective area AEff(E) defines the neutrino event rates for a given

neutrino flux (E) ( cosmic neutrinos ~ E -2 )

dN/dt = ∫ (E) AEff(E) dE

(E) NA V PEarth

Effective area and event rates

R. Gandhi et al, Phys.Rev. D58(1998), 093009

R=CC(N) CC(N)~

Correction factor for = ½() ~


Effective Area: KM3NeT vs IceCube

Neutrino effective area for KM3NeT (4) and IceCube (2).

IceCube eff. Area (arXiv:0712.3524v1, provided by A.Kappes )

KM3NeT: x 1.73 storeys/OM 8325/4800 x 3.27 photocathode area 1.73 x [21 x(0.3)2]

IceCube

KM3NeT


MC event time

Deep-sea neutrino detector: the hit rates are defined from K40

K40 hits in ANTARES MC ( K40 3545 500 )

Event time in MC : a time interval between muon hits + 2tK40

MC event time: t ~ 1 s ( at low energies )

NK40 ~ NPMT RK40 tK40 ~ 620 logN ~ 2.8

rate/PMT ±tk4o time(ns)


Preliminary limits

Physics sensitivity for diffuse neutrino flux and flux from the neutrino point sources, for E-2 . ( From S. Kuch, PhD thesis )

Upper limit (90%CL) for neutrino diffuse flux obtained for ‘reference detector’. (For 1y of data

taking) Upper limit of neutrino flux from the point sources as a function of source declination.


Summary

• MC studies in Erlangen were devoted to the KM3NeT detector optimization for CC interactions.

• For the fast comparison of the benchmark parameters for different detector configurations, only Cherenkov photons produced by were considered in simulations. • Further studies of the KM3NeT physics sensitivity (with the selected detector configuration ) should include the processes not considered in the optimization studies. For example: - CC interaction of anti-neutrinos - Cherenkov photons from the hadronic part of N interactions. - Energy estimation of reconstructed - Online filter / “KM3NeT event” model. . . . - Bkg. rejection with multi-PMT OMs. - angular resolution vs. OM time resolution.


Neutrinos from SN in KM3NeT ? - Very preliminary study, based on the simple approximations. - To be confirmed with the MC simulations.

Considered IceCube /SNEWS presentation at DPG-08, Freiburg

The SN neutrino studies for ANTARES: S. Basa, ANTARES-PHYS-1998-003. On the possibility to detect supernovae explosions with a deep underwater neutrino telescope Y. Becherini, G.Ramadoni, M.Spurio, ANTARES-PHYS-2002-002. Detection of e from Supernovae with ANTARES Study in Erlangen: A. Thurn, Supernovae detection with the ANTARES neutrino telescope


The SN Early Warning System

http://snews.bnl.gov/

The goal of SNEWS is to provide the astronomical community with a prompt alert of the occurrence of a Galactic core collapse event.

Technical description of the SNEWS: New J. Phys. 6(2004),114 [ astrpo-ph/0406214] current status: K. Scholberg, ArXiv: 0803.0531v1 ( 4 March) The SN prompt alert International network of neutrino experiments: Super-K, LVD, IceCube/AMANDA ( SNO until 2006) False alert rate of SNEWS < 1 century: Minimum acceptable level for 10s coincidence: 2 experiments, each with a false alarm rate ≤1 per week.

Expected SN rate in our Galaxy ~1-3 / century Important not to miss !

SN 1987A was the last supernova visible in our skies and the first from which scientists detected neutrinos. Hubble Heritage Team (AURA / STScI / NASA) snews.bnl.gov


Neutrinos from SN

In a core collapse of a massive star

(SN Type II) 99% of binding energy

released in :

e+e- ll l=e

neutrino energy distribution (Fermi):

The positrons are produced in an inverse reaction (electron antineutrino): e + p n + e+, [ (ep ne+) >> (ee) ] Threshold energy: E > mnp + me ~ 1.8 MeV, E> 2.1 for positrons Cherenkov photons (for n=1.33) “SN positrons” : ~ 10-15 cm/water ( K40 electrons ~ 1 cm )

Neutrino (Fermi) and Boltzmann distribution for kT=5 MeV (from A.Thurn)


The SN Neutrinos in a neutrino telescope

First suggested for AMANDA:

F. Halzen, J. E. Jacobsen and E. Zas,

Phys. Rev. D49(1994), 1758

Search for SN neutrinos in AMANDA:

Astropart. Phys. 16(2002), 345

Predicted excess of N(p.e.) in a with NOM (10s):

Veff – Effective volume per OM for AMANDA

Probability of “false SN” signal < 10-9 ( < 1 / century for t=10s interval)

SN detection significance = N/ > 6

11 - events in Kamiokande-II 2.14kton – target mass of Kamiokande-II 52 kpc - distance to SN1987A


The SN Neutrinos in a neutrino telescope

For bkg. 1pe = ( NOM R t )½ ,

Number of hits from SN neutrinos:

NS= NOM R t

SN detection significance:

NS/ = R x [( NOM /R) t )]½

Taking Veff ~ 450 m3, SN1987 type supernova

at d=8 kpc R = 10 Hz / OM (IceCube).

Veff as a function of OM number number in the AMANDA string 1.

Very small effect per OM, only R=10 Hz (factor f=1.000125 for 80kHz) is giving a significant signal in KM3NeT : ~ 10

Exp. NOM R (kHz) d (a.u.)

KM3NeT(1) 8325 80 1

IceCube(2) 4800 0.5 3.1 (1.5)

V eff ~ A x Labs

VKM3MeT ~ (1 ÷ 2) x VICeCube

Large absorption length (Labs) of IceCube is compensated by KM3NeT photocathode area (A) and QE.


KM3NeT Sensitivity to the Galactic Supernovae

AMANDA-II

AMANDA-B10

IceCube30 kpc

Number of fake SN alerts in IceCube < 15 y-1

KM3NeT (?)

The distribution f(r) of progenitor stars in the Milky Way, located within a distance r(kpc) from the Earth. ( Astropart. Phys.,16(2002), 345)

With 6 significance IceCube is sensitive to SN1987A type signal from a distance d < 30 kpc. Similar sensitivity (very preliminary ! ) of KM3NeT reference detector, d<10(20) kpc ( > 50% stars in our Galaxy )


SN detection significance

Increase signal to bkg. ratio. Decrease bkg: ( > 1/f2 ) signal: (< 1/f ) Can be studied only in the dedicated MC simulations.

For example in ANTARES-PHYS-2002-002: - 1 pe, 2 pe, 3 pe. hits/rates - coincidence rates (c1, c2) in a single storey for t = 25, 50, 100, 500 ms and 10s (Table 4) Similar studies in Erlangen: for the coincidence (c1) rates (A. Thurn)

For “Flykt-OM” more options are possible:

For example, k-hit coincidence rate from n PMTs in a storey for bkg suppression .

If p=Rotc << 1, Rk ≈ C(n,k) pk

From ANTARES PHYS-2002-002 (table 4)


Bioluminescence

Largest time varying background in KM3NeT.

- Can bioluminescence illuminate the whole KM3NeT

detector during a short time (t=10s) ?

- How often bioluminescence will give a false SN alarm ?

ANTARES data can be used for bioluminescence

analysis as an input for the MC simulations.


Summary

• First consideration indicates, that KM3NeT can detect the SN neutrinos as a significant excess of OM rates (~6) in a short time interval (~10 s) .

• If a SN false alarm rate due to bioluminescence is not too high, ( ≤ 1/week) KM3NeT can be used in the SNEWS alert network.

• MC simulations are necessary for the confirmation and studies the KM3NeT detector Galactic Supernovae detecting capabilities.

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Rezo Shanidze