Forward particle measurements at colliders and air shower development Takashi Sako High Energy Cosmic Ray Research Division, ICRR 2018/4/20 ICRR seminar 1 What I was doing before joining ICRR Forward particle measurements at colliders and air shower development What I am studying at ICRR Takashi Sako High Energy Cosmic Ray Research Division, ICRR 2 Outline • Air shower observation and hadron interaction • Forward particle measurements at collider • LHCf and RHICf experiments • Introduction to the LHCf experiment • Forward �0 and neutron results • √s dependence • RHICf • Model tuning to the LHCf result and impact on air shower simulation • Summary and future 3 High-energy cosmic ray observations • High-energy particles from outer space, cosmic rays, are observed • Majority of CRs is fully ionized nuclei Space/balloon including protons observations • 1020eV(=16J) CRs are observed Air shower observations • LHC can accelerate up to 7x1012eV Where is the origin of CRs? How are they accelerated? • Very low flux at high energy Ex) >1020eV 1 ptcl/1km2/century • Direct observation is not available => Air shower technique 4 5 High-energy cosmic ray observations • High-energy particles from outer space, cosmic rays, are observed • Majority of CRs is fully ionized nuclei Space/balloon including protons observations • 1020eV(=16J) CRs are observed Air shower observations • LHC can accelerate up to 7x1012eV Where is the origin of CRs? How are they accelerated? • Very low flux at high energy Ex) >1020eV 1 ptcl/1km2/century • Direct observation is not available => Air shower technique 6 Air shower technique • km2~1000km2 detection area is achieved using a sparse array of the ground detectors • Identification of primary particle (nuclei, gamma, etc…) is possible by measuring the difference in the air shower development • We can (want to) extract • Energy • Direction • Type (mass number, �, e-, �) of the primary particles => Analyses strongly rely on the MC Spread over 100m – few km simulation of air shower development, especially fundamental hadronic interaction is essential 7 Model dependent mass interpretation QGSJET1 QGSJETII <ln (mass number)> SIBYLL EPOS (Kampert and Unger, Astropart. Phys., 2012) • Is difference between proton and Helium small? => Factor 4 in mass number!! • Is the truth really between the existing models? => Nobody knows!! Models must be tested by accelerator data 8 Hadronic interaction in air shower proton CR proton • km2~1000km2 detection area is neutron �± achieved using a sparse array of �0 the ground detectors photon (�) Atmospheric • Identification of primary particle muon nucleus neutrino (nuclei, gamma, etc…) is possible by measuring the difference in the air shower development Electromagnetic cascade • We can (want to) extract • Energy • Direction • Type of the primary particles => Analyses strongly rely on the MC Spread over 100m – few km simulation of air shower development, especially fundamental hadronic interaction is essential 9 Hadronic interaction in air shower proton CR proton • km2~1000km2 detection area is neutron �± achieved using a sparse array of �0 the ground detectors photon (�) Atmospheric • Identification of primary particle muon nucleus neutrino (nuclei, gamma, etc…) is possible by measuring the difference in the air shower development Electromagnetic cascade • We can (want to) extract SUPER simplified view: • Energy incident particle [E] • Direction • Type -> a leading baryon [kelaEof the primary particles] + multi mesons [(1-Kela)E/Nmulti] => Analyses strongly rely on the MC Spread over 100m – few km simulation of air shower development, especially fundamental hadronic interaction is essential 10 Cosmic-ray spectrum and collision energy （D’Enterria et al., APP, 35,98-113, 2011 ） End of galactic CR and transition to extra-gal CR Ankle (GZK) cutoff: end of CR spectrum Knee: end of galactic proton CR LHC beam energy Indirect observation through air shower 11 Cosmic-ray spectrum and collision energy （D’Enterria et al., APP, 35,98-113, 2011 ） RHIC LHC FCC End of galactic CR and transition to extra-gal CR Ankle (GZK) cutoff: end of CR spectrum Knee: end of galactic proton CR 7x1012eV+7x1012eV 1017eV + (at rest) Indirect observation through air shower 12 17 Though the particle energy is 7x10 eV at LHC, the collision energy corresponds to ECR=1012 eV Detectors @ Colliders Central detector (ATLAS, CMS, ALICE, STAR, …) Beam particle (black solid) Neutral particles collision Elastic scattering Dipole （black dashed） Beam pipe ü Main physics at colliders are achieved using the “Central detectors” ü But… 13 Angular distribution at colliders multiplicity and energy flux at LHC 14TeV collisions � =0 �=1 ∘ �>1 pseudo-rapidity; η= -ln(tan(θ/2)) �<0 (�=45 ) Multiplicity Energy Flux All particles neutral ü Most of the particles are produced in the central region ü Most of the energy flows into very forward = relevant to CR air shower • forward = soft interaction; theoretical difficulty 14 • experimental difficulty Angular distribution at colliders multiplicity and energy flux at LHC 14TeV collisions pseudo-rapidity; η= -ln(tan(θ/2)) Energy Flux 1017eV proton showerElectron Profile Muon Density ] Electron Profile Muon Density 2 |η|<1 � in the 1st interaction 1<|η|<3.5 3.5<|η|<5 ] 2 Number |η|<1 10-1 5<|η|<6.6 7 6.6<|η|<8 10 1<|η|<3.5 η>8 3.5<|η|<5 Density [1/m -2 Number 10-1 5<|η|<6.6 10 6.6<| |<8 7 6 η 10 10 η>8 -3 Density [1/m 10 10-2 105 10-4 106 -3 0 200 400 600 800 1000 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 10 2 Depth [g/cm ] Distance [m] Fig. 6.1: Fraction of the air shower development for one proton induced air shower at 1017eV primary 105 ∼ 10-4 energy, which is determined� by=8 => the hadronic� 1mrad (CMS) particle production in the initial inelastic p-air collision in differentü Most of the particles are produced in the central region acceptance regions for electrons in longitudinal profile (left hand-side and muons in lateral 0 200 400 600 800 1000 0 500distribution1000ü 1500 at2000 ground2500 (right3000 hand-side).3500 4000 The4500 acceptance5000 is calculated in the center-of-mass frame of the 2 Most of the energy flows into very forward = relevant to CR air shower Depth [g/cm ] collision, and• theforward = soft interaction; theoretical difficulty shown values are relatedDistance to typical [m] LHC detectors. The major part of the air shower is determined by particle production in the forward region. 15 Fig. 6.1: Fraction of the air shower development for one proton induced• experimental difficulty air shower at 1017eV primary energy, which is determined by the hadronic particle production in the initial inelastic p-air collision The LHC data on total, elastic and diffractive cross sections and other measurements in different acceptance regions for electrons in longitudinal profilerelated to (left soft diffraction hand-side (rapidity and muons gaps, energy in lateral loss, ...) are examples of the first category, while distribution at ground (right hand-side). The acceptance is calculatedmean particle in the multiplicities, center-of-mass multiplicity frame distributions, of the jet cross sections at low p , particle ? collision, and the shown values are related to typical LHC detectors.spectra and The correlations major part between of the observables air shower belong is to the second one. determined by particle production in the forward region. 6.2.1 LHC data and hadronic interaction models For instance, measurement of the pseudorapidity dependence of the transverse energy flow and charged particle multiplicity distributions in proton-proton collisions are sensitive to the mod- The LHC data on total, elastic and diffractive crosseling of sections soft fragmentation and other effects, measurements MPI and diffractive interactions. As well as allowing for a deeper understanding of these effects in their own right, the tuning of MC models yields more related to soft diffraction (rapidity gaps, energy loss, ...)accurate are examples simulations of of the the first “underlying category, event” while - comprising MPI and additional soft interac- mean particle multiplicities, multiplicity distributions,tions jet between cross sections the primary at partons low inp events, particle with a hard perturbative scatter. The dynamics of soft interactions are also important? to understand at the LHC due to the large number of spectra and correlations between observables belong tosoft the interactions second one. (pile-up) which occur during every event. An example of how models can be retuned using these data is shown on Fig. 6.2. On the left-hand side, predictions of pre-LHC models used for air shower simulations (EPOS 1.99 [18,19] (solid line), QGSJETII-03 [21,22] 6.2.1 LHC data and hadronic interaction models (dashed line), QGSJET01 [23, 24] (dash-dotted line) and SIBYLL 2.1 [25–27] (dotted line)) For instance, measurement of the pseudorapidity dependenceare compared of the to transverse ALICE data [28], energy while flow on the and right-hand side results are presented for the two models (EPOS LHC [29] (solid line) and QGSJETII-04 [30] (dashed line)) which where charged particle multiplicity distributions in proton-protonretuned collisions using first LHC are data. sensitive to the mod- eling of soft fragmentation effects, MPI and diffractive interactions.By requiring As a forward well proton as allowing to be tagged for in a a LHC Roman pot based detector, a subset deeper understanding of these effects in their own right,of the inelastic tuning interactions of MC are models probed which yields will allow more diffraction to be investigated in more detail. This in turn will lead to more accurate tunes and possibly highlight areas of tension where the accurate simulations of the “underlying event” - comprisingcurrent phenomenological MPI and additional models are soft unable interac- to describe the data and would therefore need tions between the primary partons in events with a hardrevisiting. perturbative Such samples scatter. are especially The dynamics sensitive to the modeling of the forward regions and of soft interactions are also important to understand atwill the be of LHC use to due constrain to the cosmic-ray large air number shower physics.