cosmic neutrino background (cvb): properties and detection...

Cosmic Neutrino Background (CvB): properties and detection

perspectives

Gianpiero ManganoGianpiero Mangano

INFN, Sezione di Napoli, INFN, Sezione di Napoli, ItalyItaly

-αα

-α

-α

βαβα

βαβα

eeee+↔

↔

↔

↔

νν

νν

νννννννν

Tν = Te = Tγ

1 MeV ≤ T ≤ mµ

Relic neutrino production and decoupling

Neutrino decoupling

As the Universe expands, particle densities are diluted and temperatures fall. Weak interactions become ineffective to keep neutrinos in good thermal contact with the e.m. plasma

Rate of weak processes ~ Hubble expansion rate

MeV T MπρT G

Mπρ n , HσΓ ν

decp

RF

p

Rww 1

38

38v 2

522

2 ≈→≈→=≈

Rough, but quite accurate estimate of the decoupling temperature

Since νe have both CC and NC interactions with e±

Tdec(νe) ~ 2 MeVTdec(νµ,τ) ~ 3 MeV

At T~me, electron-positron pairs annihilate

heating photons but not the decoupled neutrinos

γγ→+ -ee

Neutrino and Photon (CMB) temperatures

1e1T)(p,f p/T +

=νν

1/3

411

TT

⎟⎠⎞

⎜⎝⎛=

ν

γ

At T~me, electron-positron pairs annihilate

heating photons but not the decoupled neutrinos

γγ→+ -ee

Neutrino and Photon (CMB) temperatures

1e1T)(p,f p/T +

=νν

1/3

411

TT

⎟⎠⎞

⎜⎝⎛=

ν

γ

Photon temp fallsslower than 1/a(t)

• Number density

• Energy density

323

3

113(6

113

2 CMBγννν Tπ

)ζn)(p,Tfπ)(pdn === ∫

⎪⎪⎪

⎩

⎪⎪⎪

⎨

⎧⎟⎠⎞

⎜⎝⎛

→+= ∫νν

νν

π

ρnm

T

)(p,Tfπ)(pdmp

i

ii

CMB

νν

43/42

3

322

114

1207

2

Massless

Massive mν>>T

Neutrinos decoupled at T~MeV, keeping a spectrum as that of a relativistic species 1e

1T)(p,f p/T +=

νν

• Number density

• Energy density

323

3

113(6

113

2 CMBγννν Tπ

)ζn)(p,Tfπ)(pdn === ∫

⎪⎪⎪

⎩

⎪⎪⎪

⎨

⎧⎟⎠⎞

⎜⎝⎛

→+= ∫νν

νν

π

ρnm

T

)(p,Tfπ)(pdmp

i

ii

CMB

νν

43/42

3

322

114

1207

2

Massless

Massive

mν>>T

Neutrinos decoupled at T~MeV, keeping a spectrum as that of a relativistic species 1e

1T)(p,f p/T +=

νν

At present 112 per flavour cm )( -3νν +

Contribution to the energy density of the Universe

eV 94.1

mh Ω i

i2

∑=ν

52 101.7h Ω −×=ν

At T<me, the radiation content of the Universe is

Relativistic particles in the Universe

γνγνγ ρππρρρ⎥⎥⎦

⎤

⎢⎢⎣

⎡⎟⎠⎞

⎜⎝⎛+=××+=+= 3114

871

15873

15

3/44

24

2

r TT

At T<me, the radiation content of the Universe is

Effective number of relativistic neutrino speciesTraditional parametrization of the energy densitystored in relativistic particles

Relativistic particles in the Universe

data) (LEP 008.0984.2 ±=νN# of flavour neutrinos:

• Extra radiation can be:

scalars, pseudoscalars, sterile neutrinos (totally or partially thermalized, bulk), neutrinos in very low-energy reheating scenarios, relativistic decay products of heavy particles…

• Particular case: relic neutrino asymmetries

Constraints from BBN and from CMB+LSS

Extra relativistic particles

At T~me, e+e- pairs annihilate heating photons

γγ→+ -ee

fν=fFD(p,Tν)[1+δf(p)]

CvB details

… and neutrinos. Non thermal features in v distribution (small effect). Oscillations slightly modify the result

( ) )(C,Em

G28p

MHpi 2W

F2

pt ρρρ +⎥⎥⎦

⎤

⎢⎢⎣

⎡−=∂−∂

νeνµ,τ

δf x102

1ep

p/T

2

+

10-2 effect

3.0460.520.520.731.3978+3ν mixing(θ13=0)

3.0460.430.430.941.3978SM

30001.40102Instantaneous decoupling

0.52

δρντ(%)

3.0460.560.701.3978+3ν mixing(sin2θ13=0.047)

Neffδρνµ (%)δρνe(%)γγ

0/TTfin

G.M. et al, NPB 729 (2005) 221

Results

Dolgov, Hansen & Semikoz, NPB 503 (1997) 426G.M. et al, PLB 534 (2002) 8

Effect of neutrinos on BBN1. Neff fixes the expansion rate during BBN

ρ(Neff)>ρ0 → ↑ 4He

38ππ H ρ

=

2. Direct effect of electron neutrinos and antineutrinos on the n-p reactions

γγ ρρρρρ ⎟⎟⎠

⎞⎜⎜⎝

⎛⎟⎠⎞

⎜⎝⎛+=++= v

effxvR N

3/4

114

871

0 2 4 6 8

-40

-20

0

20

40

60

80

7Li3He

D

4He

BBN: allowed ranges for Neff

Using 4He + D data (95% CL)

1.41.2 eff 3.1N +−=

2B10

B10 h274Ω

10/nn

η ≅= −γ

νν nn ≠

[ ]323

TT

)3(121

nnnL νν

γ

ν

γ

ννν ξξπ

ζ+⎟

⎟⎠

⎞⎜⎜⎝

⎛=

−=

⎥⎦

⎤⎢⎣

⎡⎟⎠⎞

⎜⎝⎛+⎟

⎠⎞

⎜⎝⎛=

42

2715

πξ

πξρ∆ νν

ν

Raffelt

Fermi-Dirac spectrum with temperature T and chemical potential µν=ξvTv

More radiation

CvB details

Hansen et al 2001 Hannestad 2003

Combined bounds BBN & CMB-LSS

4.2 22.001.0 , ≤≤≤− τµξξe

In the presence of flavor oscillations ?

Degeneracy direction (arbitrary ξe)

-0.2 0 0.2 0.4

ξe

-2

0

2

4

6

8

∆Nef

f

+

BBN

Evolution of neutrino asymmetries

07.0 ≤νξEffective flavor equilibrium(almost) established →

Dolgov et al 2002Wong 2002Abazajian et al 2002

07.005.0 ≤≤− ξ Serpico & Raffelt 2005

µν/Tv very small (bad for detection!)

BBN, CMB (LSS) + oscillations

µν/Tv

Hamann, Lesgourguesand GM 08

0.018 0.02 0.022 0.024 0.026 0.028 0.03

ωb

-0.2

0

0.2

0.4

ξ e

+µν/Tv

Cuoco et al 04

PLANCK

Departure from equilibrium?Pastor, Pinto Raffelt 2008

CvB for optimists

V produced by decays at some cosmological epoch

Early on: (TBBN> T>TCMB)

Late (T<< TCMB):

Unstable DM (e.g. Majoron)

dm0

v HΩΓΩ < 1.0

H0<

Γ

Lattanzi and Valle ’07

Lattanzi, Lesgourgues, GM and Valle (in progress)

Cuoco, Lesgourgues, GM and Pastor ‘05

Thermal FD spectrum

Distortion from Φdecay

ννΦ →

Present constraints from CMB (WMAP+ACBAR+VSA+CBI) and LSS (2dFGRS+SDSS) + SNIa data (Riess et al.)

Model: standard ΛCDM + nonthermal v’s

Cl and P(k) computed using CAMB code (Lewis and Challinor 2002)

Likelihoods (using COSMOMC Lewis and Bridle 2002))

3 3.2 3.4 3.6ln [1010 R

rad]

0.95 1 1.05 1.1n

0.02 0.0220.0240.026ω

b

0.15 0.2 0.25ω

dm

1.02 1.03 1.04 1.05θ

0.1 0.2 0.3τ

0.4 0.5 0.6β

0.5 1 1.5 2m

0

4 6 8 10N

eff

1 1.2 1.4 1.6 1.8q = ων (93.2 eV / m

0)

0.05 0.1 0.15A

10 20 30y

*

ΛCDM ΛCDM+R ΛCDM+NTχ2

min 1688.2 1688.0 1688.0ln[1010Rrad] 3.2±0.1 3.2±0.1 3.2±0.1ns 0.97±0.02 0.99±0.03 1.00±0.03ωb 0.0235±0.0010 0.0231±0.0010 0.0233±0.0011ωdm 0.121±0.005 0.17±0.03 0.17±0.03θ 1.043±0.005 1.033±0.006 1.033±0.006τ 0.13±0.05 0.13±0.06 0.15±0.07β 0.46±0.04 0.48±0.04 0.48±0.04m0 (eV) 0.3±0.2 0.8±0.5 0.7±0.4Neff 3.04 6±2 6±2q 1 1 1.25±0.13h 0.67±0.02 0.76±0.06 0.76±0.05Age (Gyr) 13.8±0.2 12.1±0.9 12.1±0.8ΩΛ 0.68±0.03 0.67±0.03 0.67±0.03zre 14±4 16±5 18±6σ8 0.76±0.06 0.77±0.07 0.77±0.07

TABLE I: Minimum value of the effective χ2 (defined as−2 lnL, where L is the likelihood function) and 1σ confi-dence limits for the parameters of the three models underconsideration. The first ten lines correspond to our basis ofindependent parameters, while the last five refer to relatedparameters.

CvB for pessimists

A neutrinoless Universe?

Models where v’s interact with light (pseudo)scalar particles

φφ

φφ

↔

++=

vv

chvvgvvhL jiijjiij ..

Beacom, Bell and Dodelson 2004

For the tightly coupled regime

v density strongly reduced, v’s play no role in LSS

Delay in matter domination epoch, different content in relativistic species after v decays (Neff=6.6 after decays)

couplings < 10-5 from several data (meson decay, 0ββ, SN)

Beacom, Bell and Dodelson 2004

Including CMB in the analysis:

•No free streaming (no anisotropic stress) leads to

smaller effects on LSS (for massive v’s)

change of sub-horizon perturbations at CMB epoch

•Change of sound speed and equation of state of the the titghlycoupled v - φ fluid

•v decays

larger Neff i.e. larger ISW effect for CMB

smaller effects on LSS (no v left at LSS formation epoch

Bell, Pierpaoli and Sigurdson 2005

Hannestad 2005

Massless interacting Massive decaying

Massive decaying

Usual picture of Dark Matter: cold collisionless massive particles whichdecoupled around the weak scale for freeze-out of annihilation processes

Ex: neutralino in MSSM with mass of O(100 GeV)

Difficulties:

Excess of small scale structures

Far more satellite galaxies in the Milky Way than observed (from numericalsimulation)

DM in the MeV range: SPI spectrometer on the INTEGRAL satellite observed a bright 511 KeV gamma line from the galactic bulge

Boehm, Fayet and Silk 2003−+→ eeψψ

Interacting v-DM

Framework: light (MeV) DM interacting with neutrinos

Several options for lagrangian density

Effects on cosmological scales: if DM - v’s scatterings at work duringLSS formation we expect an oscillating behavior in the power spectrum (analogous to baryon – photon fluid during CMB epoch)

G.M., Melchiorri, Serra, Cooray and Kamionkowski 2006

Equation for velocity perturbations

Effect depends upon the parameter Q

mF ∫ mDM

mF = mDM

Bounds on differentialopacity Q from SDSS data

mDM∫ mF scenario almostruled out. Requires couplingof order one

mDM = mF still viable

CvB indirect evidences

T < eVT ~ MeV

Formation of Large Scale Structures

LSS

Cosmic Microwave Background

CMB

Primordial

Nucleosynthesis

BBN

Flavor blindflavor dependent

Effect of neutrinos on BBN

1. Neff fixes the expansion rate during BBN

38ππ H ρ

=

2. Direct effect of electron neutrinos and antineutrinos on the n-p reactions

γγ ρρρρρ ⎟⎟⎠

⎞⎜⎜⎝

⎛⎟⎠⎞

⎜⎝⎛+=++= v

eff3/4

xvR N114

871

0 2 4 6 8

-40

-20

0

20

40

60

80

7Li3He

D

4He

Effect of CvB on CMB and LSSMean effect (Sachs-Wolfe, M-R equality)+ perturbations

Melchiorri and Trotta ‘04

Integrated Sachs-Wolfe effectCMB anisotropies induced by passing through a time varying gravitational potential:

( )∫ Φ−= ττδ &dTT 2

δρπ 22 4 aG=Φ∇ Poisson’s equation

• changes during radiation domination• decays after curvature or dark energy come to dominate (z~1)

CMB+LSS: allowed ranges for Neff

• Set of parameters: ( Ωbh2 , Ωcdmh2 , h , ns , A , b , Neff )

• DATA: WMAP + other CMB + LSS + HST (+ SN-Ia)

• Flat Models

Non-flat Models

• Recent result

Pierpaoli, MNRAS 342 (2003)

2.01.9eff 4.1N +−=

95% CL

Crotty, Lesgourgues & Pastor, PRD 67 (2003)

3.32.1eff 3.5N +−=

95% CL

Hannestad, JCAP 0305 (2003)

3.02.1eff 4.0N +−=

Hannestad & Raffelt, astro-ph/06071014.6N2.7 eff <<

95% CL

Allowed ranges for Neff

G.M et al, JCAP 2006

Using cosmological data (95% CL)

)-Ly and BAO( 6.2N 3.1data) LSS(CMB 7.9N 3.0

eff

eff

α+<<

+<<

2B10

B10 h274Ω

10/nn

η ≅= −γ

…but maybe in the near future ?

Forecast analysis:CMB data

Bowen et al MNRAS 2002

∆Neff ~ 3 (WMAP)

∆Neff ~ 0.2 (Planck)

Bashinsky & Seljak PRD 69 (2004) 083002Example of futureCMB satellite

New effective interactions between electron and neutrinos

Bounds on non standard neutrino interactions

Electron-Neutrino NSI

Breaking of Lepton universality (α=β) Flavour-changing (α≠ β)

Limits on from scattering experiments, LEP data, solar vs Kamland data…

RL,αβε

Berezhiani & Rossi, PLB 535 (2002) 207Davidson et al, JHEP 03 (2003) 011Barranco et al, PRD 73 (2006) 113001

Analytical calculation of Tdec in presence of NSIAnalytical calculation of Tdec in presence of NSI

Contours of equal Tdec in MeV with diagonal NSI parameters

SM SM

Neff varying the neutrino decoupling temperatureNeff varying the neutrino decoupling temperature

Effects of NSI on the neutrino spectral distortions

Here largervariation for νµ,τ

Neutrinos keep thermal contact with e-γ until smaller temperatures

3.0460.520.520.731.3978+3ν mixing(θ13=0)

30001.40102Instantaneous decoupling

3.83

δρντ(%)

3.3573.839.471.3812εLee= 4.0

εRee= 4.0

Neffδρνµ (%)δρνe(%)γγ

0/TTfin

G.M. et al, NPB 756 (2006) 100

Results

Very large NSI parameters, FAR from allowed regions

3.0460.520.520.731.3978+3ν mixing(θ13=0)

30001.40102Instantaneous decoupling

0.52

δρντ(%)

3.1201.662.211.3937

εLee= 0.12

εRee= -1.58εL

ττ= -0.5εR

ττ= 0.5εL

eτ= -0.85εR

eτ= 0.38

Neffδρνµ (%)δρνe(%)γγ

0/TTfin

G.M. et al, NPB 756 (2006) 100

Results

Large NSI parameters, still allowed by present lab data

Mixing Parameters...From present evidences of oscillations from experiments measuring

atmospheric, solar, reactor and accelerator neutrinos

A.Marrone, IFAE 2007

... and neutrino massesData on flavour oscillations do not fix the absolute scale of neutrino masses

eV

atmatm

solar

solar

eV 0.009 ∆m

eV 0.05∆m2sun

2atm

≈

≈

NO

RMA

L

INVERTED

eV

m0

What is the value of m0 ?

Direct laboratory bounds on mνSearching for non-zero neutrino mass in laboratory experiments

• Tritium beta decay: measurements of endpoint energy

m(νe) < 2.2 eV (95% CL) Mainz

Future experiments (KATRIN) m(νe) ~ 0.2-0.3 eV

• Neutrinoless double beta decay: if Majorana neutrinos

experiments with 76Ge and other isotopes: ImeeI < 0.4hN eV

eν++→ -33 eHe H

-2e2)Z(A, Z)(A, ++→

Absolute mass scale searches

< 0.4-1.6 eVNeutrinolessdouble beta decay

< 2.2 eVTritium βdecay

2/122⎟⎠

⎞⎜⎝

⎛= ∑

iiei mUm

eν

< 0.3-2.0 eVCosmology ∑i

im~

∑=i

ieiee mUm 2

Cosmological bounds on neutrino masses using WMAP3

Fogli et al., hep-ph/0608060

Dependence on the data set used. An example:

Neutrino masses in 3-neutrino schemes

CMB + galaxy clustering

+ HST, SNI-a…+ BAO and/or bias

+ including Ly-α

J.Lesgourgues & S.Pastor, Phys. Rep. 429 (2006) 307

Tritium β decay, 0ν2β and Cosmology

Fogli et al.,

hep-ph/0608060

0ν2β and Cosmology

Fogli et al., hep-ph/0608060

CvB locally: a closer look

Neutrinos cluster if massive (eV) on largecluster scale

Escape velocity: Milky Way 600 Km/s

clusters 103 Km/s

)eV/m(s/Km106m/Tcv v3

vvv ⋅≈≈

How to deal with: Boltzmann eq. + Poisson

δρπφ∆

φ2

vvxv

Ga40amf xf

=

=∇−∂+ && Sing and Ma ’02

Ringwald and Wong ‘04

Milky Way (1012 MO)

.

@ Earth

Ringwald and Wong ‘04

.

Direct detection?

Detection I: Stodolsky effect

Energy split of electron spin statesin the v background

requires v chemical potential (Dirac) or net helicity(Majorana)

Requires breaking of isotropy (Earth velocity)

Results depend on Dirac or Majorana, relativistic/non relativistic, clustered/unclustered

Duda et al ‘01)nn(sgGE vvAF −⋅≈ ⊕β∆rr

The only well established linear effect in GF

Coherent interaction of large De Brogliewavelength

Energy transfer at order GF2

∫ ∇= )x(n(x) xdGF v3

F ρCabibbo and Maiani ’82

Langacker et al ‘83

Torque on frozen magnetized macroscopic piece of material of dimension R

23

vv3

27 s cmcm 100nn

10Rcm

A10010a −

−−⊕− ⎟

⎠⎞

⎜⎝⎛ −⎟⎠⎞

⎜⎝⎛⎟⎠⎞

⎜⎝⎛⎟⎠⎞

⎜⎝⎛≈

β

Presently Cavendish torsion balances 212 s cm10a −−≈

Detection II: GF2

V-Nucleus collision: net momentum transfer due to Earth peculiar motion

2v

2FvN EG=σ

v

vNA

vv

Ep

pANvna

⊕=

=

β∆

∆σ

v

v

Tpmp

⊕

⊕

=

=

β∆β∆

25446 s cm100A)1010(a −− −≈

Zeldovich and Khlopov ’81

Smith and Lewin ‘83

Coherence enhances

mm1/m - T/1 vvv ≈≈λ3v

Ac A

NN ρλ=

Backgrounds: solar v + WIMPS

Detection III

Accelerator: vN scattering hopeless

Cosmic Rays (indirect): resonant v annihilationat mZ eV

meV10 4

m2mE

v

21

v

2Z

⎟⎟⎠

⎞⎜⎜⎝

⎛≈=

Absorption dip (sensitive tohigh z)

Emission: Z burst above GZK (sensitive to GZK volume, (50 Mpc)3)

Ringwald ‘05

18 yr10R −−≈

LHC

Question: “Is it possible to detect/measure the CvB ?”

Answer: NO !

All the methods proposed so far require either strongtheoretical assumptions or experimental apparatushaving unrealistic performances

Reviews on this subject: A.Ringwald hep-ph/0505024G.Gelmini hep-ph/0412305

A ’62 paper by S. Weinberg and v chemical potential

In the original idea a large neutrino chemical potential distortsthe electron (positron) spectrum near the endpoint energy

Massive neutrinos and neutrino capture on beta decaying nuclei

A.G.Cocco, G.Mangano and M.Messina JCAP 06(2007) 015

e±

νe

(−)

(A, Z) (A, Z ± 1)

Beta decay

e±

νe

(−)

Neutrino Capture on aBeta Decaying Nucleus

(A, Z) (A, Z ± 1)

This process has no energy threshold !

dn/dEe

Qβ

mν

Ee-me

2mν

A 2 mv gap in the electron spectrum centered around Qβ

Today we know that v are NOT degenerate but are massive !!

Beta decay

Neutrino Capture on aBeta Decaying Nucleus

dn/dEe

Ee-me

Qβ

mν

NCB Cross Sectiona new parametrization

Beta decay rate

NCB

The nuclear shape factors Cβ and Cν both depend on the same nuclearmatrix elements

It is convenient to define

In a large number of cases A can be evaluated in an exact way andNCB cross section depends only on Qβ and t1/2 (measurable)

NCB Cross Sectionon different types of decay transitions

• Superallowed transitions

• This is a very good approximation also for allowedtransitions since

• i-th unique forbidden

NCB Cross Section EvaluationThe case of Tritium

Using the expression

we obtain

where the error is due to Fermi and Gamow-Teller matrixelement uncertainties

Using shape factors ratio

where the error is due only to uncertainties on Qβ and t1/2

lim β → 0 =

lim β → 0=

NCB Cross Section Evaluation

allowed 1st unique forbidden 2nd unique forbidden 3rd unique forbidden

allowed 1st unique forbidden 2nd unique forbidden 3rd unique forbidden

β+ (bottom)β− (top) Qβ = 1 keV

Qβ = 100 keVQβ = 10 MeV

NCB Cross Section Evaluationusing measured values of Qβ and t1/2

1272 β− decays

799 β+ decays

Beta decaying nuclei having BR(β±) > 5 %selected from 14543 decays listed in the ENSDF database

3H

NCB Cross Section Evaluationspecific cases

Superallowed 0+ 0+ decaysused for CVC hypotesis testing(very precise measure of Qβ and t1/2) Nuclei having the highest product

σNCB t1/2

Relic Neutrino Detection

In the case of Tritium we estimate that 7.5 neutrino capture eventsper year are obtained using a total mass of 100 g

The cosmological relic neutrino capture rate is given by

Tν = 1.7 ⋅ 10-4 eV

after the integration over neutrino momentum and insertingnumerical values we obtain

Relic Neutrino Detectionsignal to background ratio

In the case of Tritium (and using nν=50) we found that

Taking into account the beta decays occurring in the last bin of width ∆at the spectum end-point we have that

The ratio between capture (λν) and beta decay rate (λβ) is obtainedusing the previous expressions

∼ 10- 10

Relic Neutrino Detectionsignal to background ratio

Observing the last energybins of width ∆

∆

It works for ∆<mv

dn/dTe ββ

mν Te

2mν

∆ ∆∆

where the last term is the probability for a beta decay electronat the endpoint to be measured beyond the 2mν gap

Relic Neutrino Detectiondiscovery potential

As an example, given a neutrino mass of 0.7 eV and anenergy resolution at the beta decay endpoint of 0.2 eVa signal to background ratio of 3 is obtained

In the case of 100 g mass target of Tritium it would takeone and a half year to observe a 5σ effect

In case of neutrino gravitational clustering we expect asignificant signal enhancement

FD = Fermi-Dirac NFW= Navarro,Frenk and WhiteMW=Milky Way (Ringwald, Wong)

KATRINKarlsruhe Tritium Neutrino Experiment

Aim at direct neutrino mass measurement through thestudy of the 3H endpoint(Qβ =18.59 keV, t1/2=12.32 years)

Phase I:Energy resolution: 0.93 eVTritium mass: ∼ 0.1 mgNoise level 10 mHzSensitivity to νe mass: 0.2 eV

Magnetic Adiabatic Collimator + Electrostatic filter

KATRINKarlsruhe Tritium Neutrino Experiment

MonteCarlo simulation of phase I data

First results in 2011End of Phase I data taking: 2015

Phase II:Energy resolution: 0.2 eVNoise level 1 mHz

MARE

Aim at direct neutrino mass measurement through thestudy of the 187Re endpoint (Qβ =2.66 keV, t1/2=4.3 x 1010 years)Using TEs+micro-bolometers @ 10 mK temperature

187Re crystal

TES

MARE

Energy resolution: 2÷3 eVTotal 187Re mass: ∼ 100 g

Phase II:Energy resolution: < 1 eV

vAP CollaborationCvB map 20??