HiRes 5Y HiRes 5Y Operations – Operations – Program and Program and

ContextContextWhat Physics Will be Done?What Physics Will be Done?

How Does it Compare With How Does it Compare With Other Projects?Other Projects?

General GoalsGeneral Goals

Stereo Spectrum from 10Stereo Spectrum from 1018 18 eV on –eV on – Study ankle, pileup and GZK cutoff Study ankle, pileup and GZK cutoff Confirmed energy resolution using E Confirmed energy resolution using E

pull ( E1-E2/Eav)pull ( E1-E2/Eav) Confirmed atmospheric parameters Confirmed atmospheric parameters

using energy balance and detailed using energy balance and detailed laser studies.laser studies.

Statistical strength and energy reach Statistical strength and energy reach for 5 yearsfor 5 years

Stereo Aperture and Dependence on Atmospheric Parameters

tA

ENEJ

)(

Monocular SpectrumMonocular Spectrum

Preliminary Look at Stereo Preliminary Look at Stereo Data – Energy ResolutionData – Energy Resolution

Event Energy Distribution Event Energy Distribution (> 10 EeV) – 800 hours of (> 10 EeV) – 800 hours of

stereo operationstereo operation

Preliminary Stereo Preliminary Stereo Spectrum above 10 EeVSpectrum above 10 EeV

Predicted Event Statistics Predicted Event Statistics for 5Y OPfor 5Y OP

Event Rate Prediction – Based on Event Rate Prediction – Based on Current Reconstructed Event Current Reconstructed Event

Rates (conservative)Rates (conservative) 5Y op = ~ 5000 hours5Y op = ~ 5000 hours Expect ~ 500 events > 10Expect ~ 500 events > 101919eVeV Expect ~ 5 events > 10Expect ~ 5 events > 102020 eV (based eV (based

on NSF event) ~ Eon NSF event) ~ E-3-3 spectrum spectrum Expect ~ 30 events if AGASA flux is Expect ~ 30 events if AGASA flux is

correct.(~ 5 sigma discrepancy)correct.(~ 5 sigma discrepancy) > 10> 102020 eV are “golden” – high signal, eV are “golden” – high signal,

highly constrained. highly constrained.

NSF EventNSF Event

““Golden” EventsGolden” Events

Very strong signals ( aperture cut-off due Very strong signals ( aperture cut-off due to track-length, not S/N at Xmax).to track-length, not S/N at Xmax).

If Xmax seen in both eyes, Smax balance If Xmax seen in both eyes, Smax balance can constrain/test atmospheric parameters.can constrain/test atmospheric parameters.

Events typically seen with one Rp much Events typically seen with one Rp much smaller than other – atmospheric effects smaller than other – atmospheric effects mitigated.mitigated.

If fluorescence efficiency well understood, If fluorescence efficiency well understood, very hard to significantly shift event very hard to significantly shift event energies.energies.

MEASURING FLUORESCENCE AT MEASURING FLUORESCENCE AT SLACSLAC

Extensive Air Showers (EAS) are Extensive Air Showers (EAS) are predominantly a superposition of EM sub-predominantly a superposition of EM sub-showers.showers.

Important NImportant N2 2 transition (2P) not transition (2P) not accessible by proton excitation; only e-accessible by proton excitation; only e-beam can do it.beam can do it.

FFTB beam-line provides energy FFTB beam-line provides energy equivalent showers from ~10equivalent showers from ~101515 to ~10 to ~102020 eV.eV. 101088-10-101010 electrons/pulse at 28.5 GeV. electrons/pulse at 28.5 GeV. 2% of electron pulse bremsstrahlung option.2% of electron pulse bremsstrahlung option.

Significance of pileupSignificance of pileup

No-pileup ( ENo-pileup ( E-3-3) flux implies order of ) flux implies order of magnitude decrease in integral flux magnitude decrease in integral flux between 10between 101919 and 3 x10 and 3 x1019 19 eV. (81 events – eV. (81 events – 8.1x1.7 =13 events expected )8.1x1.7 =13 events expected )

Observe 29 Stereo events above 3 x10Observe 29 Stereo events above 3 x1019 19 eV.eV. 2.9 sigma.2.9 sigma. After 5Y, expect 500 events above 10After 5Y, expect 500 events above 101919. .

Expect 50x1.7=85 events above 3 x10Expect 50x1.7=85 events above 3 x1019 19 eV eV if ( Eif ( E-3-3) flux. If present data is correct, would ) flux. If present data is correct, would see 179 events. This is a 7 sigma effect.see 179 events. This is a 7 sigma effect.

Significance of ankle ( dip Significance of ankle ( dip structure)structure)

Dip structure can be used to cross-Dip structure can be used to cross-calibrate energy scale of various calibrate energy scale of various experiments. experiments.

What is the physics of this structure? What is the physics of this structure? e+e- energy loss? Appearance of e+e- energy loss? Appearance of extragalactic spectrum?extragalactic spectrum?

Expect ~ 3000 events above 10Expect ~ 3000 events above 1018.318.3 eV and ~10,000 events above 10eV and ~10,000 events above 1018 18

eV. Statistics will not be an issue.eV. Statistics will not be an issue.

Second KneeSecond Knee

Second knee seen in many experiments. Second knee seen in many experiments. Simple energy scale shift can bring them into Simple energy scale shift can bring them into good agreement.good agreement.

Physics of transition between galactic and Physics of transition between galactic and extragalactic flux? Composition is changing in extragalactic flux? Composition is changing in this energy region.this energy region.

Can be accessed with HiRes II mono data.Can be accessed with HiRes II mono data. Propose to push thresholds down to near 10Propose to push thresholds down to near 1016 16

eV. Continuous measurement of composition eV. Continuous measurement of composition over second knee, ankle and pileup region of over second knee, ankle and pileup region of spectrum is then possible.spectrum is then possible.

Second Knee, showing correlation Second Knee, showing correlation between knee energy and spectral between knee energy and spectral

normalizationnormalization

Second Knee Spectrum, Second Knee Spectrum, Shifted to make knee come out Shifted to make knee come out

at same energyat same energy

General Goals, cont.General Goals, cont. Composition of Cosmic Rays from 10Composition of Cosmic Rays from 101818 eV eV

Xmax method – preliminary stereo results confirm Xmax method – preliminary stereo results confirm earlier Fly’s Eye results.earlier Fly’s Eye results.

Preliminary stereo results consistent with Preliminary stereo results consistent with hadronic model predictions – sensitivity to hadronic model predictions – sensitivity to composition.composition.

Expected statistics for one and two view Xmax Expected statistics for one and two view Xmax determination.determination.

Xmax resolution confirmed by Xmax pull for two Xmax resolution confirmed by Xmax pull for two view events.view events.

Search for gamma ray flux using LPM and mag. Search for gamma ray flux using LPM and mag. Brem.Brem.

Expected statistical reach.Expected statistical reach.

Resolution After All Resolution After All CutsCuts

EnergyEnergy XXmaxmax

723 Events723 Events

PullPull Distribution – Data and MCDistribution – Data and MC

) (XmaxI-XmaxII)/(XmaxI+XmaxII

Comparison of gamma ray Xmax Comparison of gamma ray Xmax distribution with LPM and distribution with LPM and

magnetic brem effects taken into magnetic brem effects taken into

accountaccount

General Goals, cont.General Goals, cont.

AnisotropyAnisotropy Small-scale anisotropy – stereo data has Small-scale anisotropy – stereo data has

symmetric error boxes and excellent symmetric error boxes and excellent angular resolution ~ 1 deg.angular resolution ~ 1 deg.

Is the AGASA auto-correlation result Is the AGASA auto-correlation result correct? HiRes I monocular data does not correct? HiRes I monocular data does not support it, but suffers from assymetric support it, but suffers from assymetric errorserrors

Sensitivity to putative point sources for 5 Y Sensitivity to putative point sources for 5 Y of operation.of operation.

Xmax viewing efficiencyXmax viewing efficiency

Integrated over energy rangeIntegrated over energy range ~60% of triggered events have Xmax ~60% of triggered events have Xmax

well reconstructed in at least one view.well reconstructed in at least one view. ~40% of triggered events have Xmax ~40% of triggered events have Xmax

well reconstructed in both views.well reconstructed in both views. Composition above 10Composition above 101919 eV will be eV will be

based onbased on

~ 300 events. Resolution function based ~ 300 events. Resolution function based on ~200 events.on ~200 events.

HiRes Monocular Error HiRes Monocular Error BoxesBoxes

HiRes monocular HiRes monocular simulated datasimulated data

HiRes Stereo simulated HiRes Stereo simulated datadata

Akeno/AGASA result on Akeno/AGASA result on anisotropy near 10anisotropy near 101818 eV eV

General Goals, cont.General Goals, cont.

Measurement of total inelastic p-Air Measurement of total inelastic p-Air cross-section.cross-section.

Composition above few x 10Composition above few x 1018 18 appears to be appears to be proton dominated.proton dominated.

Cut on deeper events to increase proton Cut on deeper events to increase proton fraction.fraction.

Xmax distribution decrement is sensitive to p-Xmax distribution decrement is sensitive to p-Air.Air.

Because result comes from tail of distribution, Because result comes from tail of distribution, understanding of resolution and reconstruction understanding of resolution and reconstruction is essential- requires tightly cut stereo data.is essential- requires tightly cut stereo data.

General Goals, contGeneral Goals, cont

Neutrino searchNeutrino search Search for unusual shower Search for unusual shower

developmentdevelopment

Other Experiments and Other Experiments and ProposalsProposals

AGASAAGASA Pierre Auger SOUTHPierre Auger SOUTH Telescope ArrayTelescope Array Pierre Auger NORTHPierre Auger NORTH EUSOEUSO OWLOWL

AGASAAGASA

100 km100 km2 2 ground array. Ran for ~ 12 ground array. Ran for ~ 12 years. To be decommissioned years. To be decommissioned ( another two years possible).( another two years possible).

Quoted accumulated aperture ~ Quoted accumulated aperture ~ HiRes I mono.HiRes I mono.

No further significant data expected.No further significant data expected.

Pierre Auger SOUTHPierre Auger SOUTH

3000 km3000 km22 ground array + Fluorescence ground array + Fluorescence detector.detector.

Ground array aperture is 7000 kmGround array aperture is 7000 km2 2 str near str near 10102020 eV. Probable completion data 2005. eV. Probable completion data 2005.

Hybrid aperture is 10% or ~700 kmHybrid aperture is 10% or ~700 km2 2 str .str . If HiRes runs for 5 years and stops in 2007, If HiRes runs for 5 years and stops in 2007,

Auger hybrid will have equal statistics in ~7 Auger hybrid will have equal statistics in ~7 years, or 2012. years, or 2012.

Southern and Northern spectra may be Southern and Northern spectra may be differentdifferent

Pierre Auger SOUTH, Pierre Auger SOUTH, cont.cont.

Ground array will have similar Ground array will have similar statistics to HiRes in 2006.statistics to HiRes in 2006.

Issues of ground array vs. Issues of ground array vs. fluorescence energy scale will not be fluorescence energy scale will not be settled until hybrid data becomes settled until hybrid data becomes significant, perhaps in 2007.significant, perhaps in 2007.

Telescope ArrayTelescope Array

Full – scale proposal for 8 stations + 2 Full – scale proposal for 8 stations + 2 HiRes stations still pending at HiRes stations still pending at Monkasho.Monkasho.

If approved, five year construction is If approved, five year construction is expected.expected.

TA phase I ( three partial eyes + TA phase I ( three partial eyes + ground array) proposal submitted to ….ground array) proposal submitted to ….

HiRes group is collaborating on both HiRes group is collaborating on both proposals.proposals.

Pierre Auger NorthPierre Auger North Originally proposed for Millard Originally proposed for Millard

County, UT.County, UT. Current status unclear – may be in Current status unclear – may be in

Europe.Europe. Unlikely to start construction before Unlikely to start construction before

2006.2006. MOU exists between HiRes, Auger MOU exists between HiRes, Auger

and TA to work together if built in and TA to work together if built in Utah.Utah.

EUSOEUSO

Phase A ESA approval for Phase A ESA approval for deployment on ISS in ~ 2009.deployment on ISS in ~ 2009.

Aperture ~ order of magnitude Aperture ~ order of magnitude larger than Auger ground array.larger than Auger ground array.

Two to three year operational life.Two to three year operational life. Similar to Auger over expected life Similar to Auger over expected life

of detectors.of detectors. Detector threshold near 10Detector threshold near 101919 eV. eV.

OWLOWL

Next generation ( post-EUSO) Next generation ( post-EUSO) proposal.proposal.

Two 1000 km orbit free-flyer Two 1000 km orbit free-flyer satellites.satellites.

Stereo observation – ~10Stereo observation – ~1066 km km22str str instantaneous aperture. instantaneous aperture.

Unlikely to fly before 2014.Unlikely to fly before 2014.