Observation of UHECRs in horizontal flux

Observation of UHECRs in horizontal flux Igor Yashin - Moscow Engineering Physics Institute for DECOR Collaboration

DECOR Collaboration M.B.Amelchakov 1, N.S.Barbashina 1, A.G.Bogdanov 1, D.V.Chernov 1, V.V.Kindin 1, R.P.Kokoulin 1, K.G.Kompaniets 1, G.Mannocchi 2, E.O.Konoreva 1, A.A.Petrukhin 1, O.Saavedra 3, V.V.Shutenko 1, D.A.Timashkov 1, G.Trinchero 2, E.E.Yanson 1, I.I.Yashin 1, O.S.Zolina 1 1. Moscow Engineering Physics Institute (Moscow, Russia) 1. Dipartimento di Fisica Generale dell Universita di Torino (Torino,, Italy) 2. Istituto di Fisica dello Spazio Interplanetario del CNR, Sezione di Torino (Torino,, Italy)

Outline Introduction Experimental setup Experimental runs 2002-2004 2004 Preliminary results Calculations (CORSIKA) Conclusions and problems

1 particle /m 2 second Direct measurements EAS detection

Direct measurements 1 particle /m 2 second EAS detection KASCADE ~ 5 10 4 m 2 Knee 1 particle/ m 2 year

Direct measurements 1 particle /m 2 second EAS detection KASCADE AGASA ~ 5 10 4 m 2 100 km 2 Knee 1 particle/ m 2 year Ankle 1 particle/ km 2 year 0 4km

Direct measurements 1 particle /m 2 second EAS detection Pierre AGASA Auger Observatory ~ 5 10 4 m 2 50 100 km km 2 Knee 1 particle/ m 2 year Ankle 1 particle/ km 2 year 1 particle/ km 2 century 3000 km 2 0 4km

Experimental complex NEVOD 9 m 2000 m 3 9 m 26 m

Experimental complex NEVOD Detection system: spatial lattice of quasispherical optical modules (QSM) up to 1500 PMTs

Coordinate detector DECOR 1992-1999 1999 Side DECOR 8 SM; 32768 channels; 70 м 2

Coordinate detector DECOR 1992-1999 1998-2002 1999 Side TOP DECOR 84 SM; 32768 19456 channels; 70 46 м 2

Coordinate detector DECOR Side coordinate detector - horizontal cosmic ray flux investigations (60-90 90 ). Systematic study of the processes of cosmic ray energy transformation including multiple muon generation in the range of interaction energies 0.1-1000 1000 PeV DECOR Surpermodule The basic element - plastic streamer tube chamber with resistive cathode coating Module - 16 chambers,, arranged in a vertical plane one above another and equipped with two-coordinate external strip readout system (256X+256Y( channels with 1.0 and 1.2 cm pitch, respectively) Supermodule (SM) - 8 such modules arranged vertically side by side

Coordinate detector DECOR Number of chambers Number of readout channels Effective area of the supermodule Total effective area Coordinate measurement accuracy Angular resolution of one supermodule 1664 52224 8.4 m 2 ~110 m 2 ~ 1 cm < 1

DECOR response Y projection X projection

DECOR response reconstruction

Experimental runs 2002-2004 2004 19 th ESRS, 3 Sep 04, Florence Main tasks: investigation of horizontal cosmic ray flux (spatial and angular distribution of muon groups, albedo muons, and so on); development of detection, event reconstruction and classification techniques. Selection of events is based on coincidences between signals from separate supermodules, and also with signals formed in external electronics system of Cherenkov detector NEVOD Period Dec 01-July 02 Dec 02- June 03 Live Time 3700 hours 3410 hours No. events ~1.5 10 8 1.6 10 8 Nov 03- June 04 3955 hours 1.6 10 8

Experimental data In total: 10580 hr live time Muon bundles of low multiplicity N µ 2; θ = 55-90 ; 6420 hr; Muon bundles of large multiplicity Two selections: 19 th ESRS, 3 Sep 04, Florence 60 º ; N µ 5; 630 hr; 2784 events 75º; N µ 10; 10580 hr; 208 events

Muon bundles of low multiplicity at large zenith angles ( (θ = 55-90 90 ) Reference track - track crosses 2 SM on two different walls of SIDE DECOR (91 10 6 events) Additional track: reconstructed in any SM and parallel to the reference one within 5 cone; d > 1 m; additional track must penetrate the detector NEVOD water volume (Е th = 1.5 7 GeV). In total 9633 selected events

preliminary 19 th ESRS, 3 Sep 04, Florence Zenith-angle dependence of ratio of muon bundles to single muons

4873:0 3644:1 3754:2 3814:3 3859:0 4199:1 3877:2 5106:3 3562:0 3149:1 3376:2 3672:3 4000:0 4098:1 4109:2 4255:3 3786:0 3732:1 3712:2 4030:3 4000:0 3388:1 3477:2 4119:3 4050:0 4120:1 4164:2 5038:3 3961:0 3769:1 3844:2 4323:3 3352:0 3438:1 3922:2 4134:3 3181:0 3942:1 5269:2 5326:3 3820:0 4458:1 4688:2 4870:3 3239:0 Near horizontal muon bundles with large multiplicity DECOR response. Event #847205 Run 242 --- Event 847205 ----05-05-2003 06:11:04.43 Trigger(1-16):01110101 00111100 Weit_Time:30.065 msec SM=0 SM=1 SM=2 SM=3 SM=4 SM=5 SM=6 SM=7 SM=8 SM=9 SM=10 19 th ESRS, 3 Sep 04, Florence 0:3923 1:3332 2:3387 3:3266 0:3054 1:3101 2:3351 3:3591 0:3570 1:3435 2:3511 3:3948 0:3619 1:3601 2:3894 3:3760 0:3750 1:3582 2:3655 3:3992 0:3641 1:3639 2:3849 3:4104 0:3609 1:3508 2:3684 3:3647 0:4245 1:3814 2:4037 3:4338 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 Plate1:Step=25nsec Plate2:Step=25nsec 0:4850 1:4191 2:3898 3:5122 0:3347 1:3879 2:3924 3:4615 0:475 1:5515 2:5367 3:6392 0:3800

Near horizontal muon bundles with large multiplicity Run 242 --- Event 847205 ----05-05-2003 06:11:04.43 Trigger(1-16):01110101 00111100 Weit_Time:30.065 msec 4873:0 3644:1 3754:2Nlam=31,N5=30,N6=31,NR1=0,NR2=0 SM=0 NGroup2=132 3814:3N1=30,N3=26 ncup= 3 SumAmp=5.57e+04 3859:0 4199:1N2=30,N4=28 ncdown= 3 NPMT=175 ETel= 0.0% ERec= 49.7% 3877:2 SM=1 5106:3 3562:0 3149:1 3376:2 SM=2 3672:3 4000:0 4098:1 4109:2 SM=3 4255:3 3786:0 3732:1 3712:2 SM=4 4030:3 4000:0 3388:1 3477:2 SM=5 4119:3 4050:0 4120:1 4164:2 SM=6 5038:3 3961:0 3769:1 3844:2 SM=7 4323:3 3352:0 3438:1 3922:2 SM=8 4134:3 3181:0 3942:1 5269:2 SM=9 5326:3 3820:0 4458:1Date=05-05-03 06:11:04.043 Nevent=847205 fm=123.1 tm=79.7 4688:2 SM=10 4870:3 3239:0 19 th ESRS, 3 Sep 04, Florence Muon bundle DECOR with 132 response. tracks. Event #847205. θ=79.7 0:3923 1:3332 2:3387 3:3266 0:3054 1:3101 2:3351 3:3591 0:3570 1:3435 2:3511 3:3948 0:3619 1:3601 2:3894 3:3760 0:3750 1:3582 2:3655 3:3992 0:3641 1:3639 2:3849 3:4104 0:3609 1:3508 2:3684 3:3647 0:4245 1:3814 2:4037 3:4338 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 Plate1:Step=25nsec Plate2:Step=25nsec 0:4850 1:4191 2:3898 3:5122 0:3347 1:3879 2:3924 3:4615 0:475 1:5515 2:5367 3:6392 0:3800

preliminary 19 th ESRS, 3 Sep 04, Florence

preliminary 19 th ESRS, 3 Sep 04, Florence Monte Carlo simulation of EAS muon component at large zenith angles Standard atmosphere CORSIKA (6.020 and 6.031) QGSJET01 (E h 80 GeV) GHEISHA2002 (E h < 80 GeV) 110 m under sea level θ 70º - CURVED option Magnetic field not included Primary protons, Fe Power low primary spectra and/or fixed energy set

Monte Carlo estimation of effective energies responsible for high multiplicity muon bundle generation CORSIKA (6.020) QGSJET01+GHEISHA2002 GHEISHA2002 Primary protons and Fe Zenith angles: 60º and 80º S det = 36 m 2 Multiplicity: 5 (θ=60( 60º ); 10 (θ( = 80º)

preliminary 19 th ESRS, 3 Sep 04, Florence Muon bundles of large multiplicity

Conclusions and problems First results of measurements of muon bundle distribution in multiplicity (spectra of local muon density) and their angular distribution at zenith angle θ > 60º are obtained. Preliminary data on the angular dependence of the ratio of intensity of muon bundles to that of single muons reveal the flattening of this ratio at zenith angles more than 84 degrees. In frame of traditional picture, for detected events the primary particles with energies in the range from 10 11 ev (single muons) and up to more than 10 17 (bundles with N µ 10 at θ > 80º) are responsible.

Conclusions and problems For quantitative analysis of obtained results, extensive simulations of expected muon group characteristics in the wide zenith angle range by means of reliably tested code are necessary. Experimental data accumulation and analysis are continued. Preliminary analysis of obtained experimental data in horizontal flux demonstrates the ability of such not large detector as NEVOD-DECOR complex to perform cosmic ray studies in a very wide energy range from 10 11 ev to more than 10 17 ev.