The ARGO-YBJ contribution to the cosmic ray physics

CRIS2010, September 2010 - Catania

Michele Iacovacci University and INFN of Naples

ARGO-YBJARGO-YBJ• Collaboration between: Collaboration between:

Istituto Nazionale di Fisica Nucleare (INFN) – ItalyIstituto Nazionale di Fisica Nucleare (INFN) – Italy Chinese Academy of Science (CAS) -ChinaChinese Academy of Science (CAS) -China

• Site:Site: YangBaJingYangBaJing Cosmic Ray Laboratory (Tibet, P.R. of China), 4300 m a.s.l.Cosmic Ray Laboratory (Tibet, P.R. of China), 4300 m a.s.l.

Site Coordinates: longitude 90° 31’ 50” E, latitude 30° 06’ 38” N

ARGO-YBJ

Experimental Hall

At present the detector is completely mounted .The central carpet of 5850 m2 is operating since July 2006 with an inclusive trigger Npad > 20, the trigger rate is about 3.7 kHz and the compressed data flow is 2.5 MB/s.

Layer (92% active surface) of Resistive Plate Chambers (RPC), covering a large area (5850 m2) + sampling guard ring

Since December 2009 Analog Readout in operation on the central carpet.

Detector Pixels

Cluster = DAQ unit Cluster = DAQ unit

= 12 RPCs= 12 RPCs

RPCRPC

StripStrip

StripStrip = =SPACE PIXEL, 6 x 62 cm2,

124800

BigPaBigPadd

BigPad =BigPad =CHARGE readout PIXEL,

120 x 145 cm2, 3120

PadPad

Pad =Pad =TIME PIXEL, 60 x 62 cm2, 15600

σt≈1 ns

Results on …-astronomy:

Crab Nebula : spectrum

Mrk421 : - continuously monitored - VHE flux correlated with X-rays - observed flares in 2006, 2008, 2010 - flare in Febuary 2010 detected in only one day

MGRO J1908+06 : measured extension and spectrum

Cosmic Rays & Particle Physics : p-p cross section Light component spectrum Large & Medium scale anisotropies Solar physics Limit on antiproton flux

7

~14 s.d. in ~800 days

NO γ/h discrimination~ 0.5 Crab/year

Crab Nebula

11211)10.055.2( 10)1/)(29.062.3( TeVscmTeVEdE

dNstat

stat

8

R.a. (deg)

≈ 6 σ

δ (d

eg)

Flux 3-4 Crab

ARGO Test Data2006 days 187-245 (110 hours)

Nhit > 60

NO Cerenkov measurements at that time

Mrk 421 the first source observed by ARGO

July 2006 flare

Full DAQ

TEST data

Mrk421 flaring activity

SWIFT

X-rays

(15-50 keV)

July 2006 June 2008 Feb 2010

ARGO test data

ARGO

Full DAQ

Mrk421 - Correlation with X-rays

2008 2009 2010

TeV rays ARGO

X- rays 2-12 KeV RXTE/AMS

X –rays 15-30 KeV SWIFT/BAT

Active period

Data sample: Nov 2007 – Feb 2010 effective time: 676 days

11.9 s.d.

Nhit > 60Integral counting rate

Ligth curve during the 2008 active period

Running average on 5 days

Daily counting rate

Nhit>100

RXTE

SWIFT

ARGO

Correlation between X-rays and gamma rays

RXTE & ARGO

Time lag = 0.11±0.55 days

Swift & ARGO

Time lag = -0.65±0.61 days

Correlation coefficient vs. time lag

Correlation analysis perfomed with DCF (Edelson & Krolik 1998)

Mrk421June 2008 flare from optical to TeV energies

data from:

GASP-WEBT (R-band) Rossi RXTE/ASM (2-12 keV) Swift/BAT (15-50 keV) SWIFT (UVOT & XRT; June 12-13) AGILE (E > 100 MeV; June 9-15) MAGIC and VERITAS (E> 400 GeV; May 27 - June 8)

No Cherenkov data after June 8

the moonlight hampered the Cherenkov telescopes measurements

Donnarumma et al. (2009)

2 flaring episodes: June 3-8 and June 9-15

Mrk 421 - June 2008 flare

ARGO

ASM/RXTE

Nhit > 100

3 days average

June 11-13

3.8

1 day average

Mrk421 – 11-13 June 2008 flare

Power law spectrum + EBL absorption :

dN/dE = (3.2 1.0) · 10-11 (E/2.5) –2.1 0.7 e-(E) ev cm –2 s –1 TeV –1

The spectrum slope is consistent with that measured by Whipple in 2000/2001 observing a similar flare

Flux (E > 1 TeV) ~ 6 Crab

G. Aielli et al. – ApJL 714 (2010) L208

General spectral features

Relation by Krennrich et al. (2002)

TeV flux vs. X-ray fluxSpectral index vs. flux

The TeV spectrum hardens increasing the flux

The relation between TeV and X-ray fluxes seems to be quadratic

4 flux ranges (RXTE): 0-2, 2-3, 3-5, >5 s-1 cm-1

Mrk421 16-18 Feb 2010

ARGO observed a strong flare on 16-18 Feb.

at 6 s.d.

Flux > 3 Crab

Peak flux (16 Feb) > 10 Crab

For the first time an EAS-array observed a TeV flare at 4-5σ on a daily basis.

VERITAS reported similar observation in Atel #2443.

16-18 Feb. 16 Feb.

17 Feb. 18 Feb.

6

MILAGRO galactic plane survey

2000-2006 data

Median energy 20 TeV

Extended source: extension < 2.6 deg

Flux 80% Crab

Abdo et al., 2007

Detected by Tibet AS-

at 4.4 s.d. (ICRC proc, 2005)

MGRO J1908+06Cygnus region

MGRO J1908+06 confirmed by HESS (2009)

Extension 0.34 deg

HESS spectrum:

dN/dE = 4.14 10-12 E-2.1 sec-1 cm-2 TeV-1

(Aharonian et al., 2009)

Inside the nebula FERMI detected a pulsar with period 106.6 ms

MILAGRO

HESS

Milagro spectrum:

dN/dE = 6.2 10-12 E-1.5 exp(-E/14.1) sec-1 cm-2 TeV-1

(Smith et al., 2009)

MGRO J1908+06 by ARGO

Intrinsic extension:

Number of events

Integral angular distribution

Nhit > 100

730.5 days

Preliminary !!!

Energy spectrum

dN/dE =(3.6 ± 0.8) 10-13 (E/ 6 TeV) –± 0.3 ph sec-1 cm-2 TeV-1

ARGO

MILAGRO

HESS

Preliminary !!!

Assumed a power law spectrum

Cutoff ?

Ec < 7 TeV

Proton-air cross section measurement

1sec)0()(

oh

eII

Use the shower frequency vs (sec -1)

The lenght is not the p interaction lenght mainly because of collision inelasticity, shower fluctuations and detector resolution.

It has been shown that = k int , where k is determined by simulations and depends on:

hadronic interactions

detector features and location (atm. depth)

actual set of experimental observables

analysis cuts

energy, ...

p-Air (mb) = 2.4 104 / int(g/cm2)

for fixed energy and shower age.

Take care of shower fluctuations

• Constrain XDO = Xdet – X0 or

XDM = Xdet – Xmax

• Select deep showers (large Xmax,

i.e. small XDM)

• Exploit detector features (space-time pattern) and location (depth).

Then:

X max

X 0

X rise

X DM

h0

Weather effects, namely the atmospheric pressure dependence on time, have been

shown to be at the level of 1 %

h0MC = 606.7 g/cm2 (4300m a.s.l. standard atm.)

h0MC / h0 = 0.988 ± 0.007

Experimental data

Clear exponential behaviour

Full consistency with MC simulation at each selection step

The proton-air cross section

Extending the energy range

with the analog readout

Phys. Rev. D 80, 092004 (2009)

Phys. Rev. D 80, 092004 (2009)

Analog read-out

0

Fs: 4000 -> 1300/m2

… can be operated at different fs. Max fs: 6500 part/m2

04000

3500

3000

2500

2000

1500

1000

500

0.1 PeV

1 PeV

A. Surdo

part/m2

part/m2

Lateral Distribution Function With tha Analog data we can study the LDF without

saturating near the core

NKG function5.42

2)1()()()( s

M

s

MM

e

r

r

r

r

r

NsCr

X. Ma, J. Zhao

r(m)

ρ(m

-2)

Unprecedented resolution at very small distances

Compare with hadint models

density

(particle/m2)

one MC eventproton, E0 378TeV, zen. 25.8°, azim. 51°, lg(χ)=3.0

one real event zen. 34.6°, azim. 133°, lg(χ)=3.3; E0~500TeV(p) or 2000TeV(Fe)

Multicore events

X. Ma, J. Zhao

Light-component spectrum of CRsLight-component spectrum of CRs

30

Measurement of the light-component (p+He) spectrum of primary CRs in the energy region (5 – 250) TeV via a Bayesian unfolding procedure

CNO < 2%

ARGO data agree with CREAM results

Evidence that the light component spectrum is flatter than in the lower

energy region

CREAM p+He EAS-TOP + MACRO

Horandel p+He

CREAM He

CREAM p

ARGO preliminary

31

Cosmic rays excess

0.06%

0.1%

N PAD > 40

584 days: 2007 Dec. – 2009 Nov.

Proton median energy 2 TeV

Smoothing radius = 5°

Intermediate scale anisotropyIntermediate scale anisotropy

9 ·1010 events

r.a.=0°

r.a.=360°

32

Proton median energy 2 TeV

ARGO-YBJARGO-YBJ

Heliotail

Geminga

Galactic Plane

~6 ·10-4 ~4 ·10-4

Proton median energy 10 TeV

MILAGROMILAGRO

Multiple explanations were proposed:Salvati & Sacco, A&A 485 (2008) 527 Drury & Aharonian, Astrop. Phys. 29 (2008) 420.K. Munakata ,AIP Conf Proc Vol 932, page 283Salvati, A&A 513 (2010) A28

Large scale anisotropyLarge scale anisotropy

Tail-in Loss-cone

Cygnus region

ARGO-YBJ DATA: 2008 and 2009

33

34

Tibet AS

M. Amenomori et.al. Science, 2006

Sun shadowSun shadow

35

Displacement of the Sun shadow

correlates with the SMMF

The displacement of the Sun shadow is a good measurement of the IMF, especially in a this particular quiet phase between 23th and 24th cycles.

Sun at maximum → shadow is washed out Sun at minimum → good shadow & SMF symmetric between NS

EW shift due to GMFNS shift due to IMF

Solar wind e IMFSolar wind e IMFradial velocity at

emission vr

+run rotation

Archimedean spiral

EARTH

x

y

… so a charge particle that passes through the IMF experience a By that changes once or twice from positive to negative (two or four sectors structure).Consenquently the sun shadow will be seen oscillating once or twice along north-south direction in a solar rotation period, or Carrington period.

Carrington period

IMF measurement with ARGO-YBJIMF measurement with ARGO-YBJ

37

time lag 1.6 days Parker model :By near the earth

Data 2006 - 2009

n Pad > 100

10 standard deviations /month

55 s.d.

PSF of the detector

3200 hours on-source

nhit > 100

The Moon shadow

Conclusions

ARGO has been taking data since Dec 2007 with duty cycle > 90%.

In the first 2 years many interesting results hve been produced.

We hope to continue good and smooth data taking whilestudies to increase sensitivity are in progress (g/h separation)

We expect better and challanging results in the coming future,Certainly some news about hadronic physics will come from analog data.

Cygnus regionCygnus region

40

VERITASMilagroFermi LAT

ARGO-YBJ

Tibet ASγ R=1.5 deg

No detection at 5σ, but with 2 years data ARGO is observing some

signals from 2 TeV sources.

• Long duration GRBs (>2s): 73• Short duration GRBs (≤2s): 10

GRB• Number of GRBs

analysed: 83• With known redshift: 14

Vulcano Workshop 2010 G. Di Sciascio 41

GRB in the ARGO FOV since Dec 2004 to Sep

2009

No evidence of coincident signal over the GRB T90 duration

In stacked analysis no evidence for any integral effect

GRBs with known redshift

Upper Limits in the 1-100 GeV Energy Range

Fluence upper limits (99% c.l.) obtained with differential spectral indexes ranging from the

value measured by satellites to2.5 . 43

West displacement of the Moon shadow caused by the Geomagnetic field

Angular Resolution

Event selection based on:

(a) “shower size” on detector, Nstrip (strip multiplicity)

(b) core reconstructed in a fiducial area (64 x 64 m2)

(c) constraints on Strip density (> 0.2/m2 within R70 )

and shower extension (R70 < 30m)

Nstrip is used to get different E sub-samples

R70: radius of circle including

70% of hits

Full Monte Carlo simulation:

Data selection (pp xsec)

Corsika showers

QGSJET I and II, SYBILL

interaction models

GEANT detector simulation