Recent results from the LHCf experiment

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1 Recent results from the LHCf experiment Gaku Mitsuka (Nagoya University) on behalf of the LHCf Collaboration ISMD 6- September, Jan Kochanowski University, Kielce

2 Outline Keywords: (Ultra high energy) Cosmic rays LHC Forward particle productions Introduction and Physics motivation Analysis results - Photon analyses at s=9gev and 7eV - π analysis at s=7ev Conclusions and Future prospects

3 Y.Muraki(Spokes person) Konan University K.Fukatsu, Y.Itow, K.Kawade,.Mase, K.Masuda, Y.Matsubara, G.Mitsuka, K.Noda,.Sako, K.Suzuki, K.aki Solar-errestrial Environment Laboratory, Nagoya University K.Kasahara, M.Nakai, Y.Shimizu, S.orii Waseda University K.Yoshida Shibaura Institute of echnology.amura Kanagawa University otally ~ collaborators O.Adriani, L.Bonechi, M.Bongi, R.D Alessandro, M.Grandi, H.Menjo, P.Papini, S.Ricciarini, G.Castellini, A. Viciani INFN, Univ. di Firenze A.ricomi INFN, Univ. di Catania A-L.Perrot CERN W.C.urner LBNL, Berkeley M.Haguenauer Ecole Polytechnique J.Velasco, A.Faus IFIC, Centro Mixto CSIC-UVEG

Energy spectra of high energy cosmic rays - sr GeV sec) Flux (m 4 - -7 ( particle/m -sec) LEAP - satellite Proton - satellite Yakustk - ground array Haverah Park - ground array Akeno - ground array

4 Energy spectra of high energy cosmic rays - sr GeV sec) Flux (m ( particle/m -sec) LEAP - satellite Proton - satellite Yakustk - ground array Haverah Park - ground array Akeno - ground array AGASA - ground array Fly's Eye - air fluorescence HiRes mono - air fluorescence HiRes mono - air fluorescence HiRes Stereo - air fluorescence Auger - hybrid ].4 yr sr ev J(E) [km.4 Standard (i.e. widely believed) model ibet&qgsje KASCADE&QGSJE AGASA, E.8 HiRes I/II Auger SD&FD, E.5 galactic (E =Z 4.5 PeV) c proton helium CNO Z 4 Z 5 stan eV Knee ( particle/m -year) 4eV Scaled flux E Energy [ev/particle] b tr e -9 7eV ( polygonato model, Hörandel, APP ()) (M. Unger ECRS 8) Extragalactic source ext - Ankle ( particle/km -year) Direct 4 ( particle/km -century) 5 Indirect Energy (ev) Energy, Composition, & direction Source of cosmic ray Structure of the universe (goal) 4

Indirect measurement of cosmic rays It is not possible to directly* measure cosmic rays above 4 ev, but possible

Composition and energy of cosmic rays affect the generation of EAS.

5 Indirect measurement of cosmic rays It is not possible to directly* measure cosmic rays above 4 ev, but possible indirectly using the cascade shower of daughter particles, i.e. Extensive Air- Shower(EAS). Composition and energy of cosmic rays affect the generation of EAS. hen understanding of high-energy cosmic ray owes to the indirect technique: comparison between the MC simulation of EAS and observation. Largest systematic uncertainty of indirect measurement is caused by the finite understanding of the hadronic interaction of cosmic ray in atmosphere. * direct measurement of cosmic ray < 4 ev is done by balloon, satellite, and ISS. Altitude [km] γ p Fe Xmax Radius [km] 5

Hadronic interactions for CR physics CERN-LHCC-6-4, 8 JINS S86. Many models exist for CR physics QGSJE (S. Ostapchenko) EPOS (K. Werner and. Pierog) etc... which address on (semi-hard) soft-qcd.

6 Hadronic interactions for CR physics CERN-LHCC-6-4, 8 JINS S86. Many models exist for CR physics QGSJE (S. Ostapchenko) EPOS (K. Werner and. Pierog) etc... which address on (semi-hard) soft-qcd. What should be measured by LHCf??. Energy spectra of γ, π and n Shower shape and µ at ground.. p spectra Shower lateral distribution at ground.. ECMS (in)dependence of the spectra Predictive power in UHE region. 4. Nuclear effects Cosmic ray interaction is NO p-p. 6

he LHCf detectors Arm 4m p-p collision at

7 he LHCf detectors Arm 4m p-p collision at s=4ev corresponds to Elab= 7 ev (~ extra-galactic source). Detectors are located at the best position to measure the large energy flow that strongly contributes the air-shower development. s=9gev and 7eV in 9- pa collisions in. Arm (W)cm x cm(h) x cm(d) Sampling calorimeter, 44X,.6λ Silicon strip detector de/dη [ev].5 p-p@4ev Arm ch~6µm ALAS/CMS LHCf/ZDC CASOR RPs η 7

8 Photon event analyses IP π, η, etc. γ Large tower Small tower (η>~) IP π, η, etc. γ Large tower Small tower (8.8<η<9.5) 8

EPOS and SIBYLL(x~) show a reasonable agreement with the LHCf data.

9 Photon analysis at s=9gev Combined data (Arm and Arm) vs MC simulations PLB 75 () 9-. None of interaction models perfectly reproduce the LHCf data. EPOS and SIBYLL(x~) show a reasonable agreement with the LHCf data. DPMJE, QGSJE and PYHIA are in good agreement Eγ<GeV, but harder above GeV ECMS dependent or independent? 9

10 Photon analysis at s=7ev PLB 7 () 8 4. Combined data (Arm and Arm) vs MC simulations Events/N ine /GeV - -5 LHCf s=7ev Gamma-ray like η >.94, Δφ = 6 Events/N ine /GeV - -5 LHCf s=7ev Gamma-ray like 8.8 < η < 8.99, Δφ = Data, Ldt=.68+nb Data, Stat. + Syst. error -8 - Data, Ldt=.68+nb Data, Stat. + Syst. error -9 DPMJE.4 QGSJE II- -9 DPMJE.4 QGSJE II- SIBYLL. SIBYLL. - EPOS.99 PYHIA EPOS.99 PYHIA 8.45 MC/Data.5 MC/Data Energy[GeV] Energy[GeV] Again, none of interaction models perfectly reproduce the LHCf data. EPOS has the smallest η-dependence relative to the LHCf data. QGSJE and SIBYLL show the somewhat large dependent on η. endencies at 9GeV are mostly same as 7eV except for QGSJE and SIBYLL.

11 π event analysis IP π γ γ Large tower Small tower (8.9<y<.) Events / ( MeV) 5 4 LHCf-Arm 9. < y < 9. - s=7ev, Ldt=.5nb Events / (.) LHCf-Arm rue EPOS s=7ev Unfolded(by 9. < y <. π +EPOS) rue spectra Unfolded(by π +PYHIA) Measured spectra Unfolded spectra(by UE-EPOS) LHCf-Arm Unfolded spectra(by UE-PYHIA) s=7ev 9.<y<. [GeV/c] p E=eV E=eV LHCf-Arm - - Measured EPOS.. E=eV Reconstructed m γγ [MeV] [GeV] P Rapidity -5

12 π analysis at s=7ev Submitted to PRD (arxiv:5.4578). MC simulations vs Combined spectra (Arm and Arm data) ] - [GeV σ/dp Ed - LHCf s=7ev π 8.9 < y < 9. - Ldt=.5+.9nb ] - [GeV σ/dp Ed - LHCf s=7ev π 9. < y < 9. - Ldt=.5+.9nb ] - [GeV σ/dp Ed - LHCf s=7ev π 9. < y < Ldt=.5+.9nb /σ inel - - Data DPMJE.4 QGSJE II- SIBYLL. EPOS.99 PYHIA /σ inel /σ inel ] - [GeV σ/dp Ed - LHCf s=7ev π 9.4 < y < Ldt=.5+.9nb ] - [GeV σ/dp Ed - LHCf s=7ev π 9.6 < y <. - Ldt=.5+.9nb ] - [GeV σ/dp Ed - LHCf s=7ev π. < y <. - Ldt=.5+.9nb /σ inel - /σ inel - /σ inel LHCf data are mostly bracketed among hadronic interaction models. DPMJE, SIBYLL(x) and PYHIA are apparently harder, while QGSJE is softer.

13 MC/Data π analysis at s=7ev LHCf MC simulations / Combined spectra (Arm and Arm data) s=7ev π 8.9 < y < 9. - Ldt=.5+.9nb DPMJE.4 QGSJE II- SIBYLL. EPOS.99 PYHIA 8.45 MC/Data LHCf s=7ev π 9. < y < 9. - Ldt=.5+.9nb MC/Data Submitted to PRD (arxiv:5.4578). LHCf s=7ev π 9. < y < Ldt=.5+.9nb MC/Data LHCf s=7ev π 9.4 < y < Ldt=.5+.9nb MC/Data LHCf s=7ev π 9.6 < y <. - Ldt=.5+.9nb MC/Data LHCf s=7ev π. < y <. - Ldt=.5+.9nb EPOS agrees well with the data among all models here. QGSJE allows only one quark exchange in collision leading is always baryon.

π analysis at s=7ev Submitted to PRD (arxiv:5.4578). σ/dp Ed /σ inel - - LHCf s=7ev π 9.4 < y < 9.6 - Ldt=.5+.

Gauss distribution E d inel hp i = K (m / ) K / (m / ) q p + m / ) dp = A exp( p / Gauss ) p Gauss Gauss 5 5 QGSJE II- (SppS) QGSJE II- (LHC) SIBYLL. (SppS) SIBYLL. (LHC) EPOS.99 (SppS) EPOS.

14 π analysis at s=7ev Submitted to PRD (arxiv:5.4578). σ/dp Ed /σ inel - - LHCf s=7ev π 9.4 < y < Ldt=.5+.9nb > [MeV] <p Average p vs Δy LHCf (this analysis) UA7 PLB 4 5 (99) - Data Exponential Gaussian [GeV/c] p. hermodynamics (Hagedron model) E d inel hp i = dp = A exp( r m. Gauss distribution E d inel hp i = K (m / ) K / (m / ) q p + m / ) dp = A exp( p / Gauss ) p Gauss Gauss 5 5 QGSJE II- (SppS) QGSJE II- (LHC) SIBYLL. (SppS) SIBYLL. (LHC) EPOS.99 (SppS) EPOS.99 (LHC) Δy Δy = ybeam - y Systematic uncertainty of LHCf data is <%. Compared with the UA7 data ( s=6gev) and MC simulations (QGSJE, SIBYLL, EPOS). Smallest dependence on ECMS is found in EPOS and it is consistent with LHCf and UA7. Large ECMS dependence is found in SIBYLL this indicates the prediction at UHE region may differ from at the LHC energy region. 4

Conclusions and Future prospects LHCf has measured the energy and transverse momentum spectrum of the forward emitted particles at the 9GeV and 7eV proton-proton collisions.

15 Conclusions and Future prospects LHCf has measured the energy and transverse momentum spectrum of the forward emitted particles at the 9GeV and 7eV proton-proton collisions. Consistent π spectra are obtained between the Arm and Arm detector. Combined spectra agree with the prediction by EPOS for the p spectra and <p>. Many analyses are ongoing: - Neutron analysis energy flow of EAS and µ at ground - Extends to other meson/baryon (e.g. η, K, Λ) 5

16 Backup 6

17 Energy spectra of high energy cosmic rays - sr GeV sec) Flux (m ( particle/m -sec) LEAP - satellite Proton - satellite Yakustk - ground array Haverah Park - ground array Akeno - ground array AGASA - ground array Fly's Eye - air fluorescence HiRes mono - air fluorescence HiRes mono - air fluorescence HiRes Stereo - air fluorescence Auger - hybrid ] [g/cm max X QGSJEII Sibyll. EPOSv.99 proton Model uncertainty Auger Direct.9eV Ankle ( particle/km -year) 4 ( particle/km -century) 5 7eV 6 7 Knee ( particle/m -year) 4eV Indirect 8 9 Energy (ev) sr - )) s - - ( E J /(m log 65 iron 8 9 UHECR Energy Spectrum UHECR Flattening Ankle 9 GZK cutoff? Auger (ICRC ) elescope Array AGASA Yakutsk HiRes I Steepening (Cutoff) HiRes II E [ev] E[eV] log (E/eV) 7 Energy, Composition, & direction Source of cosmic ray Structure of the universe (goal) 7

F dσ inela dσ dx X F Model uncertainty on Xmax.. e+8 ad-hoc A ad-hoc B.. X F. p spectra Shower lateral distribution at ground.

18 Hadronic interactions for CR physics CERN-LHCC-6-4, 8 JINS S86. Many models exist for CR physics QGSJE (S. Ostapchenko) EPOS (K. Werner and. Pierog) etc... which address on (semi-hard) soft-qcd. What should be measured by LHCf??. Energy spectra of γ, π and n Shower shape and µ at ground. F dσ inela dσ dx X F Model uncertainty on Xmax.. e+8 ad-hoc A ad-hoc B.. X F. p spectra Shower lateral distribution at ground.. ECMS (in)dependence of the spectra Predictive power in UHE region. Number of Electrons e+7 Vertical shower ad-hoc A ad-hoc B 4. Nuclear effects Cosmic ray interaction is NO p-p. Xmax(A) Xmax(B) e Vertical Depth (g/cm ) 8

19 Photon analysis at s=9gev Submitted to PLB. Cross section of the LHCf detectors Beam pipe shadow Arm Arm 9

Impact on Air-shower production Constraint of the LHCf results to CR observations is estimated by proton-air simulations: - DPMJE outputs are artificially modified to be parallel to

5x 6 ev, equivalent to the energy in lab frame of p-p collision at s=7ev Results in decrease of ~ g/cm. Events/N ine /GeV p-p at s=7ev(elab=.

20 Impact on Air-shower production Constraint of the LHCf results to CR observations is estimated by proton-air simulations: - DPMJE outputs are artificially modified to be parallel to the LHCf spectra (split a high-energy π to two low-energy π s) - Modification factor is applied to simulations of the proton-air collision. - EProton is.5x 6 ev, equivalent to the energy in lab frame of p-p collision at s=7ev Results in decrease of ~ g/cm. Events/N ine /GeV p-p at s=7ev(elab=.5x 6 ev) LHCf s=7ev Gamma-ray like η >.94, Δφ = 6 Events(/) 4 Proton-Air simulations 6 E proton =.5 ev 8 p-air at Elab=.5x 6 ev DPMJE DPMJE (Modified) Data, Ldt=nb DPMJE DPMJE (Modified) Energy [GeV] Xmax [g/cm ]

21 Fit ansatz to p spectra ] - [GeV σ/dp - LHCf s=7ev π 9. < y < Ldt=.5+.9nb Ed /σ inel - ] - [GeV σ/dp - LHCf s=7ev π 9.4 < y < Ldt=.5+.9nb Ed /σ inel - - Data Exponential Gaussian [GeV] p [GeV] p Fit/Data LHCf s=7ev π 9. < y < 9.4 Stat.+syst. uncertainty Exponential Gaussian - Ldt=.5+.9nb Fit/Data LHCf s=7ev π 9.4 < y < Ldt=.5+.9nb [GeV] p [GeV] p

22 Fit ansatz to p spectra Exponential fit Gaussian fit Numerical integration Rapidity (dof) hp i Stat. error (dof) Gauss hp i Stat. error p upper hp i Stat. error [MeV] [MeV] [MeV] [MeV] [MeV] [MeV] [GeV] [MeV] [MeV] [8.9, 9.].6 (7) (7) [9., 9.] 8. (7) (7) [9., 9.4] 8.7 (8) (8) [9.4, 9.6] 66. (6) (6) [9.6,.] 4. (5) (5) [.,.] 9. () ()

23 Scaling of the photon spectra Arm-Data Preliminary Arm-EPOS Preliminary Data at s=7ev (η>.94) Data at s=9gev Small tower :.6% Large tower : 77.4% Scaling factor :. inel d dx F <limited / inel d p dp dx F hp idp Good agreement of each XF scaling spectrum indicates a weak dependence of <p> on ECMS. Does this indicate the weak p dependence of π?

Hiroaki MENJO (KMI, Nagoya University, Japan) On behalf of the LHCf collaboration

Forward photon energy spectrum at 7TeV p-p collisions measured by the LHCf experiment Hiroaki MENJO (KMI, Nagoya University, Japan) On behalf of the LHCf collaboration ISMD 2011, Hiroshima, Japan, 26-30