A Search for Time and Angle Coincident Air Showers at CERN, Geneva Suresh Tonwar On behalf of the CORAL Collaboration 32 nd International Cosmic Ray Conference August 11-18, 2011 Beijing, China

CORAL Collaboration Germany Robert Hoffman and Joachim Prochotta, Fachhochschule Duesseldorf, Fachbereich 3, Josef Gockeln Strasse 9, D Duesseldorf India Sunil K. Gupta, Atul Jain, S. Karthikeyan, K.C. Ravindran, and S.D. Morris Tata Institute of Fundamental Research, Homi Bhabha Marg, Navy Nagar, Colaba, Mumbai Japan Yoshio Hayashi and Saburo Kawakami Faculty of Science, Osaka City University, Osaka 558 Mexico Arturo Fernandez Colegio de Fisica, Ciencias Fisico Matematicas, Un. Autonoma de Puebla, Puebla Switzerland Mario Deile, Karsten Eggert and Frej Torp Physics Division, C.e.r.N., 1211 Geneva 23 USA Suresh Tonwar University of Maryland, College Park, MD Jim Whitmore Department of Physics, Penn State University, University Park, PA 16803

Physics Motivation Witten (1984) ‘strangelets’ Massive objects in early Universe Charged objects would be accelerated in relativistic shocks just like protons and various nuclei Massive objects may break-up through interactions with matter to a large number of nucleons and nuclei Earth would experience a spray of near simultaneous shower of high energy particles spread over a very large area A large number of air showers would be generated in the atmosphere, spread over a very large area, which would be time and angle coincident Such spray of showers, detectable with small air shower arrays locally, can not be simulated by extremely high energy (~100 Eev) if the separation between the arrays is larger than a few kilometer with specified triggering conditions

Observation Strategy Operate 2 small arrays separated by 8 kilometers Each array capable of measuring arrival direction (zenith and azimuth angles) with reasonable accuracy (~2-3 degrees) and estimating primary energy (~a factor of 2) Absolute arrival time of shower known to better than a microsecond Data collection for each array with high operational efficiency to have maximum time overlap between them

Experimental system – Array at P2 (LEP/LHC, CERN) 40-detector array on the top of the building above the shaft at P2 spread over an area of 30 m x 50 m Each detector 0.5 m2 scintillator viewed by a fast photomultiplier through 1mm dia WLS fibers embedded in sigma shape 2 mm deep grooves on scintillator surface 3-line trigger, 1.05 Hz, ~100 TeV p

40-detector array at P2 (LEP/LHC, CERN)

20-detector array at P4 (LEP/LHC, CERN) 20-detector array at P4 spread over an area of 16 m x 64 m Each detector is a 1 m2 area 5 cm thick scintillator viewed by a 12.5 cm dia fast photomultiplier placed 1 m above the scintillator 3-line trigger, 0.65 Hz rate, ~ 100 TeV p

20-detector array at P4 (LEP/LHC, CERN)

Data Collection at P2 and P4 Triggers – Shower, Pedestal, Calibration Each trigger – ADC and TDC readout for each detector and Real Time clock (100 ns) readout GPS Clock – 1 Hz trigger to calibrate the RTC continually Weather Station – Atmospheric temperature and pressure recorded every 6 minutes

Data Collection : Sep 2004 – Dec 2006 Sep 22 – Dec Jun 19 – Dec 31, 2005 Jan 01 – Dec 17, 2006 Calendar time = 5.59 x 10 7 s (~ 560 days) P x 10 7 s - 93% P x 10 7 s – 86% Overlap time = 4.59 x 10 7 s

Data Collection : Sep 2004 – Dec 2006 Arrival time computed for each event using GPS calibrations ADC data converted to MIPS; ‘Particle Sum over all triggered detectors’ computed – approximate estimator for primary energy of the shower TDC data used to calculate shower arrival angle (zenith and azimuth)

Checks on Data for Each Day at P2 and P4 Data analyzed for each day separately to check for various distributions and internal consistency, at each station (P2 and P4) Variation of event rate with over 24 h Distribution of inter-event time separation Particle number spectrum for each detector Particle number sum distribution over all detectors Time difference distribution of all detectors relative to a reference detectors

Shower rate variation over 24 hours

Particle sum spectrum at P2

TDC (ns) distributions at P2 w.r.t D01

Distributions of zenith angle and azimuth angle of showers on 2006, Apr 10 at P2

Division of data into 10 independent sets ~ 55 days each

Results for data set # 5 (Jan 1- Mar 1, 2006) P2 - P4 Shower arrival time distribution P4 – P2 Shower arrival time distribution

Horizontal distance between P2 and P4 ~ 8 km Maximum time difference expected between correlated showers is ~ 8 km cos(45)/c ~ 20 us

P2 - P4 Shower Pair Arrival Time Difference Distribution (Data Set # 5) Shower rate (P2) = 1.08 Hz; Rate (P4) = 0.95 Hz Overlap time = 4.53 X 10 6 s Expected number within 30 us is 139; Observed = 125

P4 – P2 Shower Pair Arrival Time Difference Distribution (Data Set # 5) Shower rate (P2) = 1.08 Hz; Rate (P4) = 0.95 Hz Overlap time = 4.53 X 10 6 s Expected number within 30 us is 139; Observed = 137

P2-P4-P2 Shower Pair Space Arrival Angle Distributions (Data Set # 5) Showers with time separation > 30 us

P2-P4-P2 Shower Pair Space Angle Distributions (Data Set # 5) Showers with time separation < 30 us

For determination of the arrival direction (zenith and azimuth angles) of a shower, at least 5 detectors must have signals larger than the signal expected due to the passage of one or more MIP. Of the 262 shower pairs with time separation < 30 us, the arrival direction could be determined only for showers of 48 pairs. For the other pairs, one or both showers did not satisfy the above criterion. Using the space angle distribution for ‘uncorrelated’ shower pairs with time separation larger than 30 us, the expected number of shower pairs with time separation < 30 us and with space angle less than 5o is None have been observed in data set # 5.

P2-P4-P2 Shower Pair Arrival Time Difference (0-100us) Distribution (Full data)

P2-P4-P2 Shower Pair Space Angle Distribution (Full Data) Showers with time separation > 30 us

P2-P4-P2 Shower Pair Space Angle Distribution (Full Data) Showers with time separation < 30 us

Using the space angle distribution for shower pairs with time separation larger than 30 us, 1.18% of ‘uncorrelated’ shower pairs are expected with space angle less than 5 o. Therefore, 8.2 ‘uncorrelated’ shower pairs are expected with time separation less than 30 us. The observed number is 3, consistent with the absence of any statistically significant excess of shower pairs expected due to the break-up of high energy strangelets in space near the Earth. Assuming an observational area bounded by the two arrays, an observation time of 4.53 x 10 7 s and a solid angle of 2 stearadians, an upper limit of 8.1 x cm -2 s -1 sr -1 can be placed on the flux of high energy strangelets in space near the Earth.

A Search for Time and Angle Coincident Air Showers at CERN, Geneva CONCLUSIONS A search for signals due to the break-up of high energy massive objects such as ‘strangelets’, in the form of time and angle coincident air showers with 2 shower arrays located at points P2 and P4 of the LEP/LHC at CERN has yielded no statistically significant excess above the background, expected from the known cosmic ray flux. Therefore an upper limit of 8.1 x cm -2 s -1 sr -1 has been placed on the flux of high energy strangelets in space near the Earth.

Thanks for Your Kind Attention Suresh Tonwar on behalf of the CORAL Collaboration