1. RHICf experiment and Single-Spin Asymmetry Takashi SAKO (ISEE/KMI, Nagoya University) 12016/8/8 第 9 回高エネルギー QCD ・核子構造勉強会 @ 理研

2. What is RHIC forward (RHICf) experiment 2 LHCf Arm1 detector in the LHC tunnel 18m (140m at LHC) photo at PHENIX RHICf Schematic view of the RHICf installation@STAR STAR Forward region

3. Zero degree measurement at RHIC 3 RHICf Charged Particles DX magnet Neutral Particles Behind the DX magnet, charged particles are swept away, and neutral particles (photons and neutrons) arrive at the detector Detector will be installed at 18m from IP, though it was 140m in LHC Wider angle (p T ) is covered than LHC low energy collisions STAR experiment at RHIC hosts the RHICf experiment STAR Experiment

4. Two Physics Motivations of RHICf Single-Spin Asymmetry near zero degree Discovered by IP12 experiment at RHIC Detail measured by PHENIX as reported by Nakagawa-san Still open questions to be addressed Forward particle production for Cosmic-ray physics Ultra-High-Energy Cosmic Ray and atmospheric air shower Hadronic interaction and Colliders From LHCf to RHICf 4

5. Two Physics Motivations of RHICf Single-Spin Asymmetry near zero degree Discovered by IP12 experiment at RHIC Detail measured by PHENIX as reported by Minjung Still open questions to be addressed Forward particle production for Cosmic-ray physics Ultra-High-Energy Cosmic Ray and atmospheric air shower Hadronic interaction and Colliders From LHCf to RHICf 5 Start from this part, and LHCf

6. Cosmic-ray spectrum and collider energy （ D’Enterria et al., APP, 35,98-113, 2011 ） 6 FCC Knee: end of galactic proton CR End of galactic CR and transition to extra-gal CR Ankle (GZK) cutoff: end of CR spectrum LHC RHIC Indirect observation through air shower

7. 7 Air shower and hadronic interaction Cosmic rays with E>10 14 eV are observed through atmospheric air shower Energy and mass of 1ry particles are determined from the ground observations Interpretation relies on the MC simulation of air showers Hadronic interaction, especially forward particle production, is a key of the MC simulation Ground array Fluorescence light observed by telescope

8. HECR - Air shower data analysis Pierre Auger Observatory, PRD 90, 122005 (2014) 8 Analysis in high-energy cosmic-ray observations relies on air shower MC simulations Total energy, E, is measured by the total fluorescence intensity Mass is estimated by the depth of shower maximum, X max X max – E relation is totally MC basis 0g/cm 2 Xmax Proton and nuclear showers of same total energy

9. 2 ry particle flow at colliders multiplicity and energy flux at LHC 14TeV p-p collisions Energy Flux All particles neutral LHCf covers the peak of energy flow √s=14 TeV pp collision corresponds to E CR =10 17 eV 9 Multiplicity

10. ATLAS The LHC forward experiment 10 LHCf Arm#1 LHCf Arm#2 140m Neutral particles (photons and neutrons) emitted around 0 degree arrive at LHCf

11. LHCf/RHICf Detectors LHCf Arm#1 / RHICf Detector 20mmx20mm+40mmx40mm 4 XY SciFi (GSO bar)+MAPMT LHCf Arm#2 Detector 25mmx25mm+32mmx32mm 4 XY Silicon strip detectors Imaging sampling shower calorimeters Two calorimeter towers in each of Arm1 (RHICf) and Arm2 Each tower has 44 r.l. of Tungsten,16 sampling scintillator and 4 position sensitive layers 11

12. Event category of LHCf (RHICf) 12 π0π0 photon Pi-zero event (photon pair) Single photon event Leading baryon (neutron) Multi meson production Single hadron event LHCf calorimeters π0π0 photon

13. Detector performance 13 Arm2 ΔE/E < 5% ΔE/E ≈ 40%

14. LHCf/RHICf History 2004 LOI submitted to CERN 2006 TDR approved by CERN 2009 First data taking at √s=900GeV p-p collision 2010 √s=7TeV p-p collision 2013 √s=2.76TeV p-p & √s NN =5TeV p-Pb collisions 2013 RHICf LOI submitted to BNL 2014 RHICf proposal (PHENIX site) submitted to BNL 2015 √s=13TeV p-p collision 2015 RHICf proposal (STAR site) submitted to BNL, partially approved 2016 RHICf BUR submitted to BNL and approved 2016 √s NN =8.2TeV p-Pb collision 2017 RHICf √s=510GeV p+p collision 14

15. Performance at LHC 13TeV run 15 700GeV π 0 by Arm1 2 photon invariant mass In LHC 13TeV pp collision π0π0 photon

16. π 0 p z spectra in 7TeV p-p collisions (PRD accepted last week, arXiv:1507.08764 [hep-ex]) 16 Post LHC modes, QGSJET II-04 and EPOS-LHC, dessribe the data well DPMJET 3 and PYTHIA 8 over produce

17. Neutron (√s=7TeV p-p ； PLB 750 (2015) 360-366) 17 40% energy resolution is unfolded Neutral hadrons at 140m are included both in experimental data and MC High-energy peak at 0 degree is only reproduced by QGSJET II-03 Non-0 degree results are well explained by DPMJET 3 0 degree

18. to be covered in 13TeV LHCf DPM3 QGS II-04 EPOS-LHC Energy flow 18 Post-LHC models (EPOS-LHC and QGSJET II-04) well explain the π 0 results, but not for neutrons DPMJET3 explains the neutron results, but it is not recently used for CR simulations Black solid circle : LHCf data (π 0, LHCf 2012) Dotted lines : π 0 energy flow distribution of each model Thick horizontal line : Energy flow calculation after p T cut π0π0 Neutron (data contains all neutral hadrons at 140m while MC is only neutrons) rapidity (y) pseudo-rapidity (η)

19. √s scaling ; π 0 19 Scaling is important to extrapolate and interpolate for CR physics (630GeV −) 2.76TeV – 7TeV good scaling within uncertainties Wider coverage in y and p T with 13TeV data Wider √s coverage with RHICf experiment in 2017 at √s=510GeV

20. √s scaling in EPOS-LHC, 0 20 510GeV (RHIC) 7TeV (LHC) 100TeV (FCC) xFxF 7TeV / 510GeV 100TeV / 510GeV (x14 each step)

21. √s scaling; Neutron 21 PHENIX, PRD, 88, 032006 (2013) p T < 0.11 x F GeV/c √s = 30-60 GeV @ISR √s = 200 GeV @RHIC LHCf p T < 0.15 x F GeV/c √s = 7000 GeV @LHC PHENIX explains the result by 1 pion exchange More complicated exchanges at >TeV? RHICf takes data at 510GeV p+p in RUN17

22. p T (GeV/c) LHC RHIC Why not LHC 900GeV data? Maximum p T coverage is proportional to √s x F -p T coverage at LHC 7TeV and RHIC 500GeV 22 Acceptance around Zero degree RHIC allows larger with smaller √s x F -p T coverage at LHC 7TeV and RHIC 500GeV are almost identical!!

23. RHICf Installation 23 18m West from IP 10cm gap between two separating beam pipes = RHICf space Zero Degree Calorimeter behind RHICf installation space was confirmed in drawing

24. RHICf detector acceptance Widest and gapless p T coverage is realized by moving the vertical detector position. Beam pipes obscure photons but not neutrons. 87.9mm Zero degree 24 1.2GeV Acceptance in E-p T phase space Limit by beam pipe Compact double calorimeters (20mmx20mm and 40mmx40mm) Cross section view from IP Beam pipe shadow

25. RHICf Schedule Sep-Nov 2016 Test installation and commissioning of the detector and electronics Jan-Mar 2017 Commissioning of the data taking during usual collision operation May-Jun Last installation ∼ 1 week of dedicated run 25

26. Expected statistics in 12 hours 1% stat error/bin After 12 hours, high threshold energy and EM enhanced trigger to increase statistics in high energy photons and 0 26

27. SSA of forward neutron production 27 PHENIX measurements suggest p T scaling of A N Tanida et al., (PHENIX), 2011 RHIC IP12 experiment Y. Fukao, et al., Phys. Lett. B 650 (2007) 325. Kopeliovich, Potashnikova, Schmidt, Soffer: Phys. Rev. D 84 (2011) 114012.

28. Questions for SSA of forward neutron production 28 1.Measurement at p T <0.3GeV in a single √s possible by RHICf because of its 1mm position resolution for neutrons 2.Measurement at p T >0.3GeV to know A N evolution possible by RHICf because of its wide p T coverage required for cross section measurements 1 2

29. Limit in the PHENIX measurements 29 PHENIX determined the incident position using the Shower Maximum Detector (SMD) Low p T was limited by the 1cm position resolution of the detector. Neutrons hit near zero degree was not used in the analysis. Low p T was limited by the acceptance of ZDC (?) Acceptance on the detector plane Low p T limit High p T limit =1mrad => r=18mm p T ∼ E=E(r/18m)

30. Position resolutions by ZDC- SMD and RHICf for neutrons M. Togawa, PhD thesis, 2008 Kawade et al. (LHCf), JINST, 9, P03016, 2014 100GeV(x F =0.4)×3mm/18m = 0.017 GeV 30

31. RHICf detector acceptance Radial polarization (vertical asymmetry) maximizes the advantage of this wide p T coverage RHICf can detemine the direction of polarization (phase of maximum asymmetry) by its own data 87.9mm Zero degree 1.2GeV Acceptance in E-p T phase space Limit by beam pipe max asymmetry 4 hours with small tower (3mm<r<8mm) 31

32. SSA of forward neutron production 32 1.Measurement at p T <0.3GeV in a single √s possible by RHICf because of its 1mm position resolution for neutrons 2.Measurement at p T >0.3GeV to know A N evolution possible by RHICf because of its wide p T coverage required for cross section measurements 1 2

33. Summary RHICf experiment will measure very forward neutral particles at the STAR collision point Two physics motivations 1.SSA measurement in wider p T with a single √s p T scaling suggested by PHENIX can be resolved SSA up to p T =1GeV can be determined 2.Cross section measurements for cosmic-ray physics Comparing with the LHCf results, scaling in wide √s is understood 1 week of dedicated run during 510GeV p+p collision in 2017 is approved!! 33

34. Backup 34

35. Measurements KASCADE, Astropart. Phys. 2009 N e => E ; helped by air shower simulation I fluor. => E ; calorimetric, no air shower simulation, but emissivity calibration N μ -N e, E- => Mass ; helped by air shower simulation 35 energy

36. Beam Use Request for RUN17 Beam setup 2 days - * =10m to keep the beams parallel (=1.5mm at detector) 1day -Radial polarization to access p T >0.3GeV in SSA measurement 0.3-1 day [not more than 24 hours in case of any difficulty] Physics operation 2 days -12 hours data taking for minimum success both in cross section and SSA measurements in parallel Backup -we hope 24 hours data taking is assured only when we have (recoverable) trouble Timing -To be discussed, but not very early phase -Hope around May 2017 36

37. arXiv:1507.08764v1 [hep-ex] 37 RHICf coverage Why go to low energy? We can test Feynman scaling with almost identical coverage at √s = 510 GeV – 7TeV – 13 TeV