“The Cosmic Ray composition in the knee region and the hadronic interaction models” G. NavarraINFN and University, Torino, ItalyFor the EAS-TOP Collaboration

XIII International Symposium on Very High Energy Cosmic Ray InteractionsPylos Greece, 6 -12 September 2004

EAS-TOP at LNGSCampo Imperatore 2000 m a.s.l. 820 g.cm-2 data taking: 1989-2000

The Cosmic

Ray primary

spectrum

THE HIGH ENERGY GALACTIC RADIATION

KNEEDIRECT EXP.

EAS-TOP

Energy range from the direct measurements up to above the knee:Cosmic Ray primary spectrum & compositionVerification of the hadronic physics

DETECTORS:HADRONS ATMOSPHERIC C.l.ELECTROMAGNETICMUONS (E > 1 GeV)+ MUONS (E > 1.3 TeV)Deep underground GS labs.: MACRO, LVD

EAS-TOP: THE CALORIMETER& MUON TRACKER

8 x 13 cm Fe layers; 144 m2 streamer + q. proportional tubes

DETECTORS & METHODS

Hadrons p-spectrum @ E0 ~ 0.5 - 50 TeV

Cherenkov light + TeV muons p, He, CNO fluxes @ E0 ~ 100 TeV

e.m. spectrum in “knee” region E0 ~ 103 - 104 TeV

e.m. + GeV muons composition in “knee” region

e.m. + TeV muons composition in “knee” region

Verifications of methods and HE physics used

e.m. anisotropies & search for gamma primaries

CORSIKA-QGSJET

Size and energy spectra:

Ne Eo

Astrop. Phys. 10 (1999) 1

Ne-N distributions

3-component fit: L, CNO, H in LogNe = 0.2 intervals of Ne

2 = i (fci – fexp

i)2/i2 fci = wLfsL

i + wCNOfsCNOi + wHfsH

i

Simulations with = 2.75 spectraL = “p” or “50%p + 50% He” ; CNO = N; H = Fe

Frac

tion

of

even

ts

Frac

tion

of

even

ts

The composition in the ‘knee’ region

Mass group Heavier primary spectra harder Ek Z ?

l > 3.1

CNO ~ 2.75

Fe = 2.3 – 2.7

TeV muon multiplicity fits in MACRO (TeV )

L = p + He

H = Mg + Fe

L+H

Measured

EAS-TOP & MACRO (TeV )

L = p + He H = Mg + Fe

Astrop. Phys., 20 (2004) 641

< ln A > vs. E0

particle and energy flux in p-p

MACRO EAS-TOP

E. M.

The hadronic interaction models (CORSIKA)

Primary protons:

N Ne

= 0.820 ± 0.007

= 0.792 ± 0.007

= 0.789 ± 0.008

= 0.77 ± 0.02

Evolution of composition< Ne-N

EXP= 0.907 ± 0.004

EXTRCMP= 0.79 ± 0.02

MAX-VENUS= 0.820 ± 0.007

QGSJET: agreement with extrapolated direct measurements!

NO INTERACTION MODEL CAN ACCOUNT FOR THE INCREASING N vs. Ne WITHOUT INCREASING PRIMARY MASS

Component dominating at the “knee”?

He – p spectra similar RUNJOB

He spectrum harder JACEE

From “direct” measurements:JACEE

RUNJOB

JACEERUNJOBEAS-TOP

THE EAS-TOP CHERENKOV DETECTOR

2 wide angle detectors per telescope(MIRROR: A = 0.5 m2 , f.l. = 40 cm , f.o.v. = 0.16 sr)

equipped with 7 photomultipliers (d = 6.8 cm , f.o.v. = 0.023 sr)

Trigger threshold: Nphe,th = 120 phe / mirror (Ethr 40 TeV at r = 130 m) Trigger rate: 7 Hz/telescopeCherenkov event: coincidence in T = 30 ns , between any 2 corresponding PMs.

5

MACRO UndergroundGran Sasso Labs.depth: 3100 m w.e. Eth ~ 1.3 TeV 76.6 x 12 x 4.8 m

< 1o

20 m at surface level

Astrop. Phys., 21 (2004) 223

Proc. 28th ICRC, 1 (2003) 115

A different approach: EAS-TOP & MACRO

EAS-TOP (Cherenkov detector):

total energy through the amplitude

of the detected Cherenkov light signal.

MACRO (muondetector):

EAS primaries with En > 1.3 TeV/n

EAS geometry through the track

( r ~ 20 m, ~ 10 uncertainties)

MACRO and EAS-TOP are separated by 1100-1300 m of rock: E 1.3 - 1.6 TeV

DATA SET

t = 7s

September 1998 – May 2000

Tot. Time T = 208 h

5 telescopes

exposure 830 day m2 sr

angular window:

: 16 < < 58 , 127 < <

210

MACRO events in T and :

35814

with EAS-TOP in t = 7s:

3830

(expected accidental events < 3.0)

Event coincidence is established

off-line (GPS system - T < 1s)

Coincidence Peak

tMACRO–t Cherenkov (s)

t = 7s

7

E ≈ 80 TeV Np ≈ N

He

E ≈ 250 Tev Np ≈ N

He ≈ NCNO

C.l. yield: p ~ He ~ CNO

p

He

CNO

Fe

C.l. + TeV muon analysis

Mg

p, He, CNO @ ~ 100-200 TeVInformation EAS-TOP

& MACROJACEE RUNJOB

Jp+He

(80 TeV)

18 ± 4 12 ± 3 8 ± 2

Jp+He+CNO

(250 TeV)

1.1 ± 0.3 0.7 ± 0.2 0.5 ± 0.1

Jp/ Jp+He

(80 TeV)

0.29 ± 0.09 0.45 ± 0.12 0.63 ± 0.20

Jp+He/ Jp+He+CNO

(250 TeV)

0.78 ± 0.17 0.70 ± 0.20 0.76 ± 0.25

JHe

(80 TeV)

12.7 ± 4.4 6.4 ± 1.4 3.1 ± 0.7

x 10-7 m-2s-1sr-1TeV-1

EAS-TOP & MACRO data

EAS-TOP & MACRO data + p-flux

p+He p+He+CNO

The Cherenkov light LDF

WITH JACEE FLUX

Test of energy release in the atmosphere of QGSJET:

R = (42 m) / (134 m)

= Ne (370 g/cm2) / Ne (505 g/cm2)

(Rexp – Rth)/Rth = 0.14 ± 0.09

Ne and N spectra

Ne N

Sec Ik*107 Nk chi**2/df m-2s-1sr-1

1.00-1.05 2.56 2.96 0.06 1.1 0.1 6.08 0.03 7.8/111.05-1.10 2.56 2.86 0.05 1.3 0.2 5.95 0.04 8.4/111.10-1.15 2.56 2.84 0.04 1.0 0.1 5.95 0.04 5.3/111.15-1.20 2.56 2.82 0.08 0.8 0.2 5.92 0.06 7.6/111.20-1.25 2.56 2.92 0.09 0.5 0.1 5.94 0.05 4.6/111.25-1.30 2.56 2.75 0.07 1.4 0.4 5.62 0.07 2.8/11

chi**2/df (1slope)1.00-1.05 3.21 0.06 3.42 0.10 1.2 0.3 4.65 0.10 10.4/10 18.7/121.05-1.10 3.18 0.08 3.45 0.10 1.4 0.2 4.65 0.10 9.3/10 20.7/121.10-1.15 3.18 0.09 3.40 0.20 0.6 0.2 4.75 0.15 6.9/10 9.9/121.15-1.20 3.12 0.15 3.4 0.10 1.6 0.5 4.55 0.15 5.9/10 14/12

Agreement inside errors (~ 30%)

2 slopes

Decreasing with increasing zenith angle

Ne

N

N Ne

= (e –1) /(-1) = 0.7 – 0.8

In agreement with models SAME BENDING COMPONENT ?

IFSAME BENDING COMPONENTin Ne and N spectra

We can identify it.

We construct for each component (p, He, CNO, Mg, Fe) the energy spectrum fitting the size spectrum in the region of the knee.

From such energy spectra we construct for each component the corresponding N spectrum, to be compared with the measured one.

The result of such comparison

Muon size spectrum: measured and expected for different primaries

on the base of the Ne spectrum

If “Knee” on Helium primaries

Ek (He) = (3.5 0.3) 1015 eV

VENUS

QGSJET

NEXUS

The primary spectrum from EAS-TOP

Natural evolution…..

KASCADE-Grande

KASCADE-Grande

If : E k,Z = Z * E k,1

SEARCH FOR IRON “KNEE” AT ~ 1017 eV

PRIMARY COMPOSITION: 1016 - 1018 eV

STUDY OF C.R. INTERACTIONS AT UHE

N (> 1018 eV) ~ 250 (3 y data taking)

At the threshold of Auger (High Resolution)

P,He

iron

Eknee = 3 – 4 PeV

EAS-TOP/KASCADE

Hadron spectrum at 820 g/cm2 & comparison with sea level (1033 g/cm2)

Calculated QGSJET

Exp. KASCADE/EAS-TOP

E0 = 0.5 – 50 TeVProton spectrum at TOP

Astrop. Phys. 19 (2003) 329 He contribution subtracted

S(Eo) = (9.8 1.1stat 1.6sys) 10–5 (Eo/1000) –2.80 0.06 m-2 s-1 sr-1 GeV-1