The measurement of the average shower development profile

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The measurement of the average shower development profile. Apr. 28, 2008. Contents. Introduction Measurement method Data sample Average development profile Uncertainty analysis Discussion and Conclusion. Introduction EAS. Nmax. Xmax. - PowerPoint PPT Presentation

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  • The measurement of the average shower development profile

    Apr. 28, 2008

  • Contents IntroductionMeasurement methodData sampleAverage development profileUncertainty analysis Discussion and Conclusion

  • IntroductionEASAnatomy of an air shower initiated by a high energy protonNmaxXmaxA simulated shower longitudinal development profileTo measure shower longitudinal development profile with HiRes stereo data

  • Introduction: MotivationThe shower shape of development profile is very important for energy reconstruction

    Empirical shower development function are based on data at lower energy or based on theoretical electromagnetic cascade calculation

    None of them has been experimentally tested at these energies in the atmosphere (above 1018eV)

    The profile with energy between 1017-1018eV has been tested by HiRes/MIA experiment

    It is necessary to measure the profile at higher energy with HiRes stereo data

  • The HiRes experiment HiRes1 & HiRes:22 (42) Mirrors azimuth angle: 0-3600, elevation angle: 3-17 (3-31) electronics: H&S (FADC)began operation in June, 1997 (Dec 1999).End : Apr. 2006HiRes experiment:located at the U.S. Army Dugway proving grounds in UtahA fluorescence detector Two sites: HiRes1 & HiRe2Data analysis mode: Monocular and stereo

  • MethodSo, Cerenkov light is not proportional to the number of charge particles in each stepSubtract the Cerenkov light, convert the signals into shower sizes (correction).Measured signals: Fluorescence lightproportional to the number of charge particles & isotropyDirect Cerenkov lightMainly along with shower directionAccumulated Scattered Cerenkov light (Cerenkov beam)Rayleigh scatterMie scatter

  • Measurement methodDetermine Xmax and Nmax by a local fitNormalize showers & align them together according to shower ages

    Average shower sizes in age bins Size(X) = size(X) / Nmaxs = 3X/(X+2Xmax)

  • Data sample HiRes stereo data: 1999.12-2005.11

    Cuts are used as following: angle: > 135o Zenith angle: > 60o Shower slant depth span: depth < 250g/cm2 Shower Xmax is not seen by the detector

    2095 events are survived with clear profiles & minimum Cherenkov light contaminations

  • The average profile The average shower longitudinal development profile (the dots) and fitting functions.

  • X0 is the initial point, Nm is the shower maximum,Xm is shower maximum location, is the shower decay lengthTm = Xm/ , T0 = X0/ Where y = Xm/L0, T = X/L0, L0 is the radiation length, about 36.66g/cm2 Gaisser-Hillas functionGreisen functionGaussian-in-Age functionwhere is the width of showerX sN/Nm n

  • Uncertainty analysis

    Cherenkov light subtraction: assuming a Cherenkov light contamination of 4.0% and 8.0% in the first bin

    Atmospheric condition: average atmospheric conditionDaily atmospheric parameters

    The shape of profile has no noticeable change

  • Discussion: shower width vs. XmaxShower widths dependence on shower XmaxDATAMCSigma=-0.021*xmax/100+0.356Sigma=-0.018*xmax/100+0.339Sigma=-0.015*xmax/100+0.312Correlation coefficient: 88%Correlation coefficient: 27%Correlation coefficient: 50%

  • Discussion: energy resolutionEnergy resolution has improvement, especially the big tail vanished

  • Discussion: shower width vs. Energy

  • Conclusion Gaisser-Hillas, Greisen and Gaussian-in-Age functions describe the average profile equally well.

    The integrals of three functions are all lower than that of data by about 1.5%.

    The widths of showers have dependence on their Xmax

  • Gaisser-Hillas functionWhere X0 is the initial point, Nm is the shower maximumXm is shower maximum location is the shower decay lengthX sN/Nm nTm = Xm/ , T0 = X0/

  • Greisen functionGreisen function describes the development of a pure electromagnetic air shower Where y = Xm/L0, T = X/L0, L0 is the radiation length, about 36.66g/cm2

  • Gaussian-in-Age functionwhere is the width of shower

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