Study of Forbush decreases with a WC detector Luis Villaseñor in collaboration with Angelica Bahena UMSNH Symposium CINVESTAV-UNAM In memoriam Augusto Garcia ICN, December 1,2009

Cosmic rays (1912) Forbush effect (1937)

Can we see the Forbush effect with a single WCD? Auger (muons)~ 4% (ICRC 2009) McMurdo (neutrons)~ 15%

Detectors  Volume 1m height by 1.15m diameter.  We use a tyvek bag  PMT: EMI 8 in to get  Difuse reflection Two water tanks

Detectors Tipical muon Amplitude ~150 mV ~200 MeV Our threshold 22 mV ~0.15 VEM

Stopping muon at 0.1 VEM Decay electron at 0.17 VEM = 41 MeV Crossing muon at 1 VEM Alarcón M. et al., NIM A 420 [1-2], (1999). Auger, NIM 2006 Water Cerenkov Detector

Water Cerenkov Detector

H.Salazar and L. Villasenor, NIM 2005 Water Cerenkov Detector

Electronics We started with two setups CAMAC Discriminator Amplificator Scalers GPIB LabView

Electronics GPS Custom-made ADC Pressure and temperature sensors FPGA + VHDL Serial port, Linux tools

Electronics One reason Why We prefered Our custom FPGA-based Electronics Baseline Changed Rate did not Change Because our Thresholds Are anchored To the baseline Inside the FPGA Besides Programming FPGAs is fun!

Raw Data

Data analysis: Anticorrelation Between R and P Data from October, 2009

Data analysis: Anticorrelation Between R and P Data from November, 2009

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Data Analysis

Corrected Data

Comparison with neutron detector data

Conlusions Stable operation of WCD FPGA-based electronics performs well Good anti-correlation of rate with atmospheric pressure at the 0.5% level Our periodic variations <~1% Sensitive to variations > 2% We will take data during the upcoming period of solar activity T he answer to our initial question: Yes, provided the sun cooperates