Muon measurements and hadronic interactions at the Pierre Auger Observatory

Transcription

1 Muon measurements and hadronic interactions at the Pierre Auger Observatory Raul Sarmento for the Pierre Auger Collaboration Rencontres de Moriond - VEHPU, La Thuile, 22 nd March 2017

2 Pierre Auger Observatory Cosmic ray 1st interaction high in the atmosphere Fig. 1. The Auger Observatory. Each Fig. dot 1. corresponds The Auger Observatory. to one of the Each 1660 Fig. dot 1. surface corresponds The Auger detector Observatory. tostations. one of the The Each 1660 four dot surface fluorescence corresponds detector detector tostations. one ofen t of view of its six telescopes. Alsoof shown view of areits the sixtwo telescopes. laser facilities, Alsoof shown CLF viewand of areits XLF, the sixnear two telescopes. laser the Observatory facilities, Also shown CLF center. and arexlf, the near two laser the Obse fac Shower development: right ascension [13,14]. The right upp impose stringent constraints impos on electromagnetic and muonic The Auger data provide Th e between arrival directionsbetwe of co cascades positions of AGNs with z o positi 0:01 Fully efficient: E > 18.3 ev Hybrid detector Pierre Auger Collaboration / Nuclear Instruments and Methods in Physics Research A 798 (2015) Collaboration also has performe Collab air cross-section at 57 TeV air [19] cro t of the cross-section towards of the h proton proton cross-section, proto wh the best extrapolation from thethe b composition measurements comp cou from light to heavier nucleifrom if cu describe well the air shower descri ph Upper limits have been obtai Up above an energy thresholdabove whic down models [25,26]. Also, down c published [27 29], as well publis as sea [30,31]. [30, to the Assembly Building for replaponents. urface detector operates using solar ol board incorporates protection cirr the monitoring of the solar power g for orderly shutdown and wakeup of an extended cloudy period during inadequate solar power available to usly. The solar power system has not od long enough to require shutting echarging. The most probable battery, and batteries are changed during c boards are the most critical elethey are subject to very severe temperature variations, humidity, re rate of the PMTs is about 20 per igh voltage (HV) module and base ed as well as some problems due to ailures except those concerning the otocathode) can be repaired in the 1.2. Observatory design FD - longitudinal profile Fig. 6. FD building at Los Leones during the day. Behind the building is a communication tower. This photo was taken during daytime when shutters were opened because of maintenance O Design targets for the surface De cycle, a well-defined aperture cycle, inde measurement of the time measu struct particles, sensitivity to showers partica contained detector stations and contai in by cosmic ray muons. The fluores by cos 19 every event above ev arrivin every recorded by at least onerecord fluor measurement of the longitudina measu synchronization for simultaneous synch SD - lateral profile

3 Pierre Auger Observatory and hadronic interactions Particle physics beyond the LHC energy scale: E p > 19 ev E c.m. > 0 TeV Phys. Rev. Lett. 9, (2012) Λ η 2 = 55.8 ± 2.3 g/cm E < 18.5 ev - high proton fraction and statistics /g] 2 dn/dx max [cm 1 The tail of the X max distribution is dominated by the distribution of the first interaction depths the exponential shape of the t dn=dx max / expð X max = Þ, X max [g/cm 2 ] 3

4 Pierre Auger Observatory and hadronic interactions Particle physics beyond the LHC energy scale: E p > 19 ev E c.m. > 0 TeV Phys. Rev. Lett. 9, (2012) (Proton-Proton) [mb] σ inel ATLAS 2011 CMS 2011 ALICE 2011 TOTEM 2011 UA5 CDF/E7 This work (Glauber) QGSJet01 QGSJetII.3 Sibyll2.1 Epos1.99 Pythia Phojet From proton-air to proton-proton interaction: Glauber model Proton-proton inelastic cross section derived at E c.m. = 57 TeV 30 3 s [GeV] 4 4 5

5 Muon production in extensive air showers Muons in EAS are probes of hadronic interactions and carry information on the primary mass (b) Heitler-Matthews model p Neutral pions feed the electromagnetic cascade n=1 Charged pions decays feed the muonic cascade π + _ π o n=2 X max ln(e/a) N μ E β A 1-β n=3 β is elasticity and multiplicity dependent 5

6 Muon production in extensive air showers Full EAS simulations using the leading hadronic interaction models: EPOS-LHC, QGSJET-II.0.4, Sybill Phenomenological approaches (diffraction, fragmentation, inelastic intermediate states, nuclear effects, QCD saturation, etc.) where accelerator data is unavailable Tuned after LHC data 6

7 Auger muon measurements 1) Muon production depth Phys. Rev. D 90, (2014) & Phys. Rev. D 92, (E) (2015) 2) Mean number of muons in highly inclined showers Phys. Rev. D 91, (2015) 3) Hadronic shower size Phys. Rev. Lett. 117, (2016) 7

8 Muon production depth Phys. Rev. D 90, (2014) & Phys. Rev. D 92, (E) (2015) Assumption: muons produced in shower axis travel in straight lines From the muon arrival time to the muon production depth 8 z 1 r 2 2 cðt ht ε iþ cðt ht εiþ X μ ¼ Z z ρðz 0 Þdz 0 ; þ Δ hz π i

9 Muon production depth Inclined showers with muon-rich signal at ground - SD measurement: θ ϵ [55, 65 ] r > 1700 m MPD reconstruction efficiency increases with the number of muons per event: E > 19.3 ev From the muon production depth distribution to X μ max - composition-sensitive variable 9

10 Muon production depth 600 proton Test hadronic models with mass limits from cosmic ray abundances ] 2 [g/cm µ max X Significant differences among model predictions 450 iron Epos-LHC E [ev] QGSJetII Data points in the region of heavy mass

11 Muon production depth For a given model, translate X μ max and X max into atomic mass A µ 8 Xmax 8 7 X max 7 6 QGSJetII-04 6 Epos-LHC 5 5 lna 4 Fe lna 4 Fe p 1 0 p E [ev] E [ev] 20 X max independent measurement with FD: consistency between electromagnetic and muonic shower components? 11

12 Number of muons in inclined Phys. Rev. D 91, (2015) showers Measurement of the muon content Highly inclined showers for high muon purity: θ ϵ [62, 80 ] Lateral muon profile from SD stations signal, using maximumlikelihood method based on muon density templates Surface integration to get total number of muons at ground: R μ (normalized to energy and reference value muons) 12 FIG. 1. Expected number of muon hits per SD station as predicted by the reference profile ρ μ;19, for θ ¼ 80 and ϕ ¼ 0, in cylindrical coordinates around the shower axis. The radial density roughly follows a power law in any given direction. The quadrupole structure is generated by charge separation in Earth s magnetic field. The weaker dipole structure is caused by projection effects and muon attenuation. Early (late) arriving particles are on the right (left) side in this projection.

13 Number of muons in inclined showers PHYSICAL REVIEW D 91, (2015) 13

14 Number of muons in inclined showers Model predictions with small differences Main sources of systematic uncertainty: absolute energy scale and SD response to inclined muons 14

15 Number of muons in inclined showers h i Combination with X max information highligths inconsistent shower description 15

16 Number of muons in inclined showers Simulation of proton-iron mixture with a mean logarithmic mass that matches <X max > from FD 16

17 Hadronic shower size Phys. Rev. Lett. 117, (2016) To reproduce the higher signal in data: increase the number of muons in simulations by or increase the Auger energy scale by a similar factor on models. We observe 30 to 80% þ17 20 ðsysþ% del. The estimated defi Analysis method to measure the hadronic shower size that removes the sensitivity to the absolute energy calibration includes data from vertical showers 17

18 Hadronic shower size Region of small mass composition change: E ϵ [ 18.8, 19.2 ] ev 411 hybrid events de/dx [PeV/(g/cm 2 ] Proton Sim Energy: (13.8 +_ 0.7) EeV Iron Sim Zenith: ( _ 0.2 ) o Data X Max : (752 +_ 9) g/cm 2! 2 /dof (p) = 1.19! 2 /dof (Fe) = 1.21 Eliminate the effect of shower-toshower fluctuations: for each data event, find simulations that match the longitudinal profile Depth [g/cm 2 ] Proton Sim Iron Sim Data Excess in signal is evident in the shower lateral profile S [VEM] 1 Consider S(00) - shower size at 00m Radius [m]

19 Hadronic shower size θ ϵ [0, 60 ] All models and composition hypotheses: data/sim ratio increases with zenith angle Signal with hadronic origin dominates the region of maximum excess To explore the signal excess angular dependence S [VEM] Total Pure Muon Pure EM EM from µ Decay EM from Had. Jet µ from Photprod sec(θ)

20 Hadronic shower size Electromagnetic shower sizes scales with energy: R E Hadronic rescaling: R had R E α for hadronic signal slower evolution with energy, α=0.9 Þ S resc ðr E ;R had Þ i;j R E S EM;i;j þ R had R α E S had;i;j: Rescale the simulated signal (event i, mass j) R E and R had best fit values from maximizing the likelihood function: i P i p j prior probability for mass j, given X max,i Q P i ¼ X j p j ðx max;i Þ (Sresc ðr E ;R had Þ i;j Sð00Þ i ) 2 qffiffiffiffiffiffiffiffiffiffiffi exp 2πσ 2 2σ 2 : i;j i;j ð2þ 20

21 Hadronic shower size R had Systematic Uncert. QII-04 p QII-04 Mixed EPOS-LHC p EPOS-LHC Mixed R E No energy rescaling needed; hadronic rescaling with a corresponding muon excess of 1.33 ± 0.16 (1.61 ± 0.21) at 2.1 (2.9) sigma for EPOS-LHC (QGSJet-II-04) 21

22 Summary and Outlook Auger muon measurements: muon production depth mean number of muons in highly inclined showers hadronic shower size vs energy rescaling ME# # Primary#cosmic# ca:on#through#muons# Results are in tension with expectations from LHC-tuned hadronic interaction models ns # Accelerator data in the forward or#on#top#of#the#tank#to# region for model builders directly#e.m.#shower# upgrade scintillators on nt# topaugerprime: of the Cherenkov tanks asures#e.m.#+#muons# Measurement of the electromagnetic to:# component at ground e#primary#iden:fica:on## Improve the shower description and enhance the primary identification e#shower#descrip:on# #systema:c#uncertain:es# 22 8

23 Muon measurements and hadronic interactions at the Pierre Auger Observatory Thanks for the attention! Acknowledgments: Rencontres de Moriond - VEHPU, La Thuile, 22 nd March 2017