konstantin belov high resolution fly’s eye (hires) collaboration

Konstantin Belov. GZK-40, Moscow.Konstantin Belov. GZK-40, Moscow.

Konstantin Belov Konstantin Belov High Resolution Fly’s Eye (HiRes) High Resolution Fly’s Eye (HiRes)

CollaborationCollaboration

GZK-40. INR, Moscow.May 17, 2006.

<Xmax> measurements by fluorescence <Xmax> measurements by fluorescence experimentsexperiments..

Columbia UniversityColumbia UniversityUniversity of AdelaideUniversity of AdelaideUniversity of New University of New MexicoMexicoRutgers UniversityRutgers UniversityUniversity of MontanaUniversity of MontanaLos Alamos National Los Alamos National LaboratoryLaboratoryUniversity of TokyoUniversity of Tokyo


MotivationMotivation

Compare the <Xmax> measurements from the Compare the <Xmax> measurements from the three fluorescence experiments: Fly’s Eye, three fluorescence experiments: Fly’s Eye, HiRes/MIA, and HiRes Stereo.HiRes/MIA, and HiRes Stereo.Only fluorescence experiment SEE Xmax.Only fluorescence experiment SEE Xmax.In HiRes energy range (10In HiRes energy range (1017.217.2-10-1020.520.5 eV) expect to eV) expect to see a transition between galactic and see a transition between galactic and extragalactic sources:extragalactic sources:– Expect highest energy galactic cosmic rays to be heavy nuclei (iron);Expect highest energy galactic cosmic rays to be heavy nuclei (iron);– Expect extragalactic cosmic rays to be light (protons)Expect extragalactic cosmic rays to be light (protons)– Expect transition from mixed to light composition.Expect transition from mixed to light composition.


XXmaxmax distribution for p, CNO, Fe distribution for p, CNO, Fe

Heavier primaries Heavier primaries develop earlier in the develop earlier in the atmosphere.atmosphere.RMS of the XRMS of the Xmax max

distribution is different.distribution is different.

QGSJetQGSJet


Elongation rate p, CNO, FeElongation rate p, CNO, Fe


Fly’s Eye detector. Fly’s Eye detector.

Two fluorescence detectors were positioned 3.5 km Two fluorescence detectors were positioned 3.5 km apart;apart;The effective energy range extended from 10The effective energy range extended from 101717 eV to eV to 3310101919 eV; eV;555 degree pixel size;5 degree pixel size;Geometry of the event was determined by the Geometry of the event was determined by the intersection of the two event-detector planes;intersection of the two event-detector planes; Elevation angle range from 0 to 90 degrees;Elevation angle range from 0 to 90 degrees;FE II had only partial azimuth coverageFE II had only partial azimuth coverage


HiRes prototype/MIAHiRes prototype/MIA

Hybrid fluorescence - muon array detector;Hybrid fluorescence - muon array detector;Fourteen mirror prototype of the current HiRes detector Fourteen mirror prototype of the current HiRes detector had a 1had a 11 degree pixel size; looked from 3 to 71 1 degree pixel size; looked from 3 to 71 degrees in elevation.degrees in elevation.Was located 3.5 km from the center of the MIA muon Was located 3.5 km from the center of the MIA muon array;array;The muon array sampled a part of muon lateral The muon array sampled a part of muon lateral distribution. 3 km effective area;distribution. 3 km effective area;Energy range from 5Energy range from 510101616 eV to just above 10 eV to just above 101818 eV; eV;Event geometry was determined by using the HiRes Event geometry was determined by using the HiRes event-detector plane and timing from both detectors.event-detector plane and timing from both detectors.


HiRes fluorescence detector.HiRes fluorescence detector.


Stereo observations.Stereo observations.HiRes 1 has 20 operational HiRes 1 has 20 operational

mirrors in one ring. S/H mirrors in one ring. S/H electronics. FOV 3-17electronics. FOV 3-17º in º in elevation, elevation, 322322º in azimuth º in azimuth

HiRes 2 has 42 operational HiRes 2 has 42 operational mirrors in two rings. FADC mirrors in two rings. FADC electronics. FOV 3-31electronics. FOV 3-31º in º in elevation, elevation, 336336º in azimuth.º in azimuth.

Detectors are 12.6 km apart Detectors are 12.6 km apart forming a stereo pair.forming a stereo pair.

Stereo fixes shower geometry Stereo fixes shower geometry improving resolution.improving resolution.

Idealistic view of a stereo event


An event of the HiRes displays.An event of the HiRes displays.

HiRes1 – one ringHiRes1 – one ringdetectordetector

HiRes2 – two ringHiRes2 – two ringdetectordetector


Measured shower profile.

Event by event:Event by event:XXmaxmax in g/cm in g/cm22;;Total energy of the primary Total energy of the primary particle:particle:Arrival directionArrival direction

Statistically:Statistically:pp-air inelastic cross-section;-air inelastic cross-section;Mass composition.Mass composition.

Measured shower parameters.


HiRes stereo and HiRes/MIA data.HiRes stereo and HiRes/MIA data.

HiRes/MIA - hybrid HiRes/MIA - hybrid experiment. Resolution experiment. Resolution function estimated from function estimated from simulations ~ 44 gm/cmsimulations ~ 44 gm/cm22

HiRes stereo - XHiRes stereo - Xmax max

resolution measured, 30 resolution measured, 30 gm/cmgm/cm22


Fly’s Eye stereo data.Fly’s Eye stereo data.

Fly’s Eye Stereo - XFly’s Eye Stereo - Xmaxmax resolution ~45 gm/cmresolution ~45 gm/cm2 2 measured resolution measured resolution functionfunction


Systematic errorsSystematic errors

All three experiments quote systematic errors ~ 25 All three experiments quote systematic errors ~ 25 gm/cmgm/cm22..Dominant contributionsDominant contributions– Mirror surveyMirror survey– Cherenkov subtractionCherenkov subtraction– Atmospheric profileAtmospheric profile– Aerosol correctionsAerosol corrections

Highest energy data is best measurementsHighest energy data is best measurements- most complete profile- most complete profile- minimum Cherenkov subtraction- minimum Cherenkov subtraction


Comparison of Fly’s Eye Stereo and HiRes Comparison of Fly’s Eye Stereo and HiRes energy scalesenergy scales

Energy scale for all three Energy scale for all three experiments is consistent experiments is consistent (location of ankle and second (location of ankle and second knee).knee).


Elongation rateElongation rate

Use HiRes stereo average XUse HiRes stereo average Xmax max

and Fly’s Eye stereo average and Fly’s Eye stereo average Xmax above 10Xmax above 1018 18 eV.eV.

Require a 13 gm/cmRequire a 13 gm/cm22 upward shift upward shift for Fly’s Eye to bring means for Fly’s Eye to bring means into agreementinto agreement

Shift all Fly’s eye XShift all Fly’s eye Xmaxmax data points data points by the same amount.by the same amount.

Filled circles, HiRes; Triangles,HiRes/MIA, Open circles, Fly’s Eye (shifted).


Elongation RateElongation Rate

Simple shift of Fly’s Eye data brings all data into Simple shift of Fly’s Eye data brings all data into reasonable agreement.reasonable agreement.Fly’s Eye and HiRes data are in excellent Fly’s Eye and HiRes data are in excellent agreement above 10agreement above 101818 eV. eV.HiRes/MIA shows earlier transition to “protons”, HiRes/MIA shows earlier transition to “protons”, but point by point discrepancy is small.but point by point discrepancy is small.HiRes/MIA systematics are better understood, HiRes/MIA systematics are better understood, however.however.


What about XWhat about Xmaxmax distributions? distributions?

Are Xmax distribution widths consistent?Are Xmax distribution widths consistent? Two overlap regionsTwo overlap regions

- Fly’s Eye and Hires/MIA in 3x10- Fly’s Eye and Hires/MIA in 3x101717 to 5 x 10 to 5 x 1017 17 eV bin.eV bin. - Fly’s Eye and HiRes stereo in > 10- Fly’s Eye and HiRes stereo in > 1018 18 eV bin.eV bin.

No evidence of discrepancy in distribution widths.No evidence of discrepancy in distribution widths.


Triangles: Fly’s Eye Stereo; Triangles: Fly’s Eye Stereo; Circles: HiRes/MIA.Circles: HiRes/MIA.

Fly’s Eye vs HiRes/MIA Xmax at 3-5 x 1017 eV


Triangles: Stereo Fly’s Eye; Circles: HiRes.

Fly’s Eye vs HiRes Xmax > 1018 eV


Sequence of XSequence of Xmaxmax distributions in three distributions in three increasing energy bins 3-5increasing energy bins 3-510101717, 5-10, 5-1010101717

and > 10and > 101818eV.eV.

Red-Fly’s EyeRed-Fly’s EyeBlue-HiRes/MIABlue-HiRes/MIAPurple-HiRes stereoPurple-HiRes stereo


ConclusionsConclusions

A simple XA simple Xmaxmax shift brings all three experiments shift brings all three experiments into reasonable agreement.into reasonable agreement.Widths of XWidths of Xmaxmax distributions are in agreement. distributions are in agreement.

Normalized XNormalized Xmaxmax distribution show change to distribution show change to wider distribution above 10wider distribution above 101818, consistent with , consistent with change to protons.change to protons.Interpretation of elongation rate over limited Interpretation of elongation rate over limited energy range is problematic - Need large energy range is problematic - Need large dynamic range in a single experiment!dynamic range in a single experiment!

konstantin belov high resolution fly’s eye (hires) collaboration

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