Spin and Cosmology Physics Opportunity Using RHICf Korea-Japan PHENIX collaboration meeting 2015 년 10 월 19 일 타니다 키요시 (JAEA/ 서울대 )

Project overview A new experiment at RHIC to measure very forward (  < 5 mrad) particles ( ,  0, n) in pp collisions at √s=500 GeV (and pA collisions) ～ 1800cm 10cm D x magnet blue beamyellow beam ZDC RHICf detector Here Run expected in 2017 (& more)

RHICf science Hadron/particle physics –Left-right spin asymmetry in forward neutron Cosmic-ray science: –Calibrate hadronic interaction –Most energy goes forward –One of the major sources for systematic uncertainty

Hadron/Particle physics How most forward particles are produced in pp collisions? –High energy, yet non-perturbative (p T < 1 GeV/c) Regge theory? –Explains total cross section in high-energy pp collision with Pomeron –How about observables other than total cross section?

Forward n – OPE model E.g.: N. N. Nikolaev et al., PRD 60, (1999) OPE models seem OK (x F )   a 2 pnpn BG

Left-right asymmetry (forward = beam direction, up = spin direction) Need both helicity flip & non-flip amplitudes In Regge theory –Pion exchange gives spin flip –Non flip? Other reggeons? Sensitive to mechanism 6 Single spin asymmetry A N

PHENIX observation Significant A N found near 0 deg. 7

What we want in RHICf Observed A N is larger for larger  s Can be interpreted as p T dependence p T ~ (  s/2) ・ x F ・  (Note: A N = 0 at p T = 0) We want to have data for higher p T –To what p T, A N increases linearly? –Helps to identify Reggeon that gives non-flip amplitude RHICf: can cover larger angle –Up to  ~5 mrad, p T ~ 1 GeV/c –pA collision case is interesting, too. –Also, A N of  and   can be measured

Cosmic-ray Science What is the origin?? –A 100 year-old problem since its discovery in 1912 Low energy -- sun How is it accelerated? –Supernova remnant up to eV –Beyond that? Where does it come from? –From our galaxy? Extragalactic? What is the composition? –Proton? Heavier nuclei, up to Fe? Many questions remain especially for highest energy

How do they measure? Air shower

Fluoresence Scintillation from nitrogen + Cherenkov light Seen by usual telescope + PMT Full calorimetry + 3D position Dark night only

Surface detectors Count number of charged particles (muon) at the ground surface Sampling measurement, but all day/night

Hybrid measurement Coincidence of SD + FD –SD gives absolute position & timing –Full shower observation with FD

Energy spectrum

Features A kink (“Ankle”) at eV and a sharp cut-off around eV are now established GZK (Greisen-Zatsepin-Kuz’min) mechanism? –Energy loss of proton by p +  (    N +  where  is CMB (cosmic microwave background) photon –The proton energy threshold with 1 meV photon is 7×10 19 eV. Change of nuclide? Change of source? –p vs A; galactic vs extra-galactic Limit of acceleration mechanism? –Highest energy is limited by source size & B-field Breakdown of special relativity???

Energy scale issue Different experiments do not agree in absolute flux –calibration issue –~20% uncertainty  ~40% flux uncertainty Analysis of the same events by SD/FD shows 27% difference –Systematic correction for SD data  Air shower development is not well understood!

Calibration at collider Uncertainty in interaction  Uncertainties in energy scale (especially in SD), X max, and so on. p/A with well known energies are available at LHC and RHIC –Proton equivalent energy up to s/2m p =10 17 eV Highest energy not reachable? –Scaling helps –Cross-section can be approximately given by x F (E/E max ) and p T (transverse momentum, << E) alone. –Scaling violation should be checked with different energies  Measurements at LHC & RHIC

Experiments in LHC

RHICf setup & run plan Import LHCf detector and install it in front of ZDC Detector moves up/down by manipulator –Increases angle coverage Expect to run in 2017 –Beamtime: ~ 1 week –More runs later? ～ 1800cm 10cm D x magnet blue beamyellow beam ZDC RHICf detector Here

Zero degree detector and acceptance p T (GeV/c) LHC RHIC 26

From the Large Hadron Collider to the Longisland Hadron Collider 27 LHCf Arm1 detector in the LHC tunnel Schematic view of the RHICf installation 18m (140m at LHC) ZDC Frontend Support photo at PHENIX RHICf

LHCf Arm1 Detector => RHICf Detector LHCf Arm1 Detector 20mmx20mm+40mmx40mm 4 XY GSO bar hodoscope Imaging sampling shower calorimeters Two calorimeter towers Each tower has 44 r.l. of Tungsten,16 sampling scintillators and 4XY pairs GSO bar hodoscope Sensitive to photons, neutrons and photons from π 0 28

29 RHICf coverage vertically movable ZDC IP limited by beam pipe View from IP ZDC size 0 degree p T < 0.7 GeV/c p T < 1.4 GeV/c Detector moves up-down; wide p T coverage and to avoid ZDC interference x F -p T coverage identical to LHC 7TeV collision Wider coverage and higher resolution in p T than ZDC measurements (joint analysis between ZDC and RHICf)

Requested Beam Condition 30 1day for β * setup, 1 day for polarization direction, 1 day for physics + contingency => 5 days of dedicated time needed to reduce beam divergence to measure up-down asymmetry Cross section measurement approved. Asymmetry measurement (polarization setup) pending

Time line for RUN17 PHENIX closes in RUN2017 for sPHENIX upgrade Discussion with STAR to define cabling, support structure and electronics installation on going (they are supportive)

STAR in 2015 summer 32 Complex structure with pp2pp roman pot and radiation shield Installation and manipulating method under discussion Common analysis with central detector, pp2pp roman pots, ZDC

Summary RHICf – A new experiment at RHIC at a cross-field of nuclear/particle physics and cosmic-ray science Hadron/particle physics –Production mechanism for forward particles in high energy pp collision? –Measure A N of forward neutrons up to p T ~ 1 GeV Cosmic-ray science –Energy calibration – input for interaction models –Similar p T coverage with LHCf at lower √s  Test of x F scaling Setup – LHCf detector will be installed to RHIC(STAR) –Expected to run in 2017 for a week

Backup slides