Polarized DIS with Future Polarized Colliders Abhay Deshpande
Polarized DIS with Future Polarized Colliders Abhay Deshpande RIKEN BNL Research Center (RBRC) Precision Lepton-Nucleon Scattering: HERA III Workshop Munich, December 18 th, 2002 December 18, 2002 RIKEN BNL RESEARCH CENTER Physics Opportunities at Future Polarized Colliders
Overview • Introduction to different proposals under consideration for polarized DIS • Physics opportunities with: -- Polarized HERA, Electron Ion Collider (EIC) at BNL -- Tesla*HERA (THERA) + TESLA-N/ELFE@DESY • Status of Polarized Colliders at BNL -- Status and comments on EIC -- Status of polarized proton beam acceleration & collisions at BNL • Summary December 18, 2002 Physics Opportunities at Future Polarized Colliders 2
Deep Inelastic Scattering • Observe scattered electron/muon & hadrons in current jets • Observe spectator or remnant jet December 18, 2002 Physics Opportunities at Future Polarized Colliders 3
Why Collider in the Future? • Past polarized DIS experiments: MOSTLY FIXED TARGET • Collider has distinct advantages --- Confirmed at HERA • Better angular separation between scattered lepton & nuclear fragments Better resolution of electromagnetic probe Recognition of rapidity gap events (recent diffractive physics) • Better measurement of nuclear fragments • Higher center of mass (Co. M) energies reachable • Tricky integration of beam pipe – interaction region -- detector December 18, 2002 Physics Opportunities at Future Polarized Colliders 4
Projects Under Consideration Machine Lumi/Year Sqrt(s) Tesla-N (fix target) ELFE at DESY 100+ fb-1 10 -30 Ge. V ~10 Ge. V EIC 4+ fb-1 20 -100 Ge. V Pol. HERA 150 pb-1 300 Ge. V Pol. THERA 40 -250 pb-1 1 -1. 5 Te. V • Pol. HERA needs polarized protons (Siberian Snakes, polarimeters etc. ), Use existing detectors(? ) • EIC needs a polarized electron accelerator facility at RHIC & a new detector • THERA & TESLA-N & ELFE need TESLA and polarized protons in HERA & a new detector What Physics? Luminosity? CM Energy? December 18, 2002 Physics Opportunities at Future Polarized Colliders 5
Kinematic Coverage ELFE: Q 2 max~ 102 Ge. V 2 xmin ~ 10 -2 (1 Ge. V 2) 20 -100 Ge. V TESLA-N: Q 2 max~ 103 Ge. V 2 xmin ~ 10 -3 (1 Ge. V 2) EIC: Q 2 max~ 104 Ge. V 2 xmin ~ 10 -4 (1 Ge. V 2) HERA: Q 2 max~ 105 Ge. V 2 xmin ~ 10 -5 (1 Ge. V 2) THERA: Q 2 max~ 106 Ge. V 2 xmin ~ 10 -6 (1 Ge. V 2) EIC overlaps with the fixed target experiments because of the changeable beam energies December 18, 2002 Physics Opportunities at Future Polarized Colliders 6
Luminosity Vs. Center of Mass EIC has variable: -- beam energies -- polarized light nuclear species 100 times HERA luminosity Collisions 2010(? ) TESLA-N HERA has: -- 3 times larger CM Collisions 2007(? ) THERA December 18, 2002 Physics Opportunities at Future Polarized Colliders TESLA-N/THERA -- Need the DESY LC -- Low/High CM -- High/Low Luminosity Collisions 2015(? ) 7
Scientific Frontiers: Future DIS Experiments • Nucleon Structure: polarized & unpolarized e-p/n scattering -- Role of quarks and gluons in the nucleon -- Unpolarized quark & gluon distributions -- Spin structure: polarized quark & gluon distributions -- Correlation between partons hard exclusive processes leading to Generalized Parton Distributions (GPD’s) • Nuclear structure: unpolarized e-A scattering EIC e-A Physics -- Role of quarks and gluons in nuclei -- e-p vs. e-A physics in comparison • Hadronization in nucleons and nuclei & effect of nuclear media -- How do partons knocked out of nucleon in DIS evolve in to colorless hadrons? • Partonic matter under extreme conditions -- e-A vs. e-p scattering; study as a function of A December 18, 2002 Physics Opportunities at Future Polarized Colliders Unpolarized Low x Issues: A. Caldwell 8
All of them at EIC & Pol. HERA Some at TESLA-N/ELFE Polarized DIS at Future Facilities • Spin structure functions g 1 (p, n) at low x, high precision -- g 1(p-n): Bjorken Spin sum rule better than 1% accuracy • Polarized gluon distribution function DG(x, Q 2) -- at least three different experimental methods • Precision measurement of a. S(Q 2) from g 1 scaling violations • Polarized structure function of the photon from photo-production • Electroweak structure function g 5 via W+/- production • Flavor separation of PDFs through semi-inclusive DIS • Deeply Virtual Compton Scattering (DVCS) Gerneralized Parton Distributions (GPDs) • Transversity • Drell-Hern-Gerasimov spin sum rule test at high n • Target/Current fragmentation studies • … etc…. DESY-PROC-1999 -03 & EIC White-Paper BNL-Report-68933 (Feb. 2002) December 18, 2002 Physics Opportunities at Future Polarized Colliders 9
A. D. & V. W. Hughes EIC WS at Yale’ 00 Spin structure function g 1 at low x Polarized HERA Polarized EIC ~5 -7 days of data 3 years of data Studies included statistical error & detector smearing to confirm that asymmetries are measurable. No present or future approved experiment will be able to make this measurement December 18, 2002 Physics Opportunities at Future Polarized Colliders 10
Polarized Gluon Measurements • This is the hottest of the experimental measurements being pursued at various experimental facilities: -- HERMES/DESY, COMPASS/CERN, E 159/E 160 at SLAC -- Low scales poses a potential problem for interpretation -- TESLA-N? -- RHIC Spin (polarized p-p) -- Issues of non-DIS scattering • Deep Inelastic Scattering kinematics of EIC/HERA -- Scaling violations (p. QCD analysis at NLO) of g 1 -- (2+1) jet production in photon-gluon-fusion process -- 2 -high p. T hadron production in PGF (TESLA-N) • Photo-production (real photon) kinematics at EIC/HERA -- Single and di-jet production in PGF -- Open charm production in PGF December 18, 2002 Physics Opportunities at Future Polarized Colliders 11
A. D. , V. W. Hughes & J. Lichtenstadt EIC WS, Yale’ 00 DG from Scaling Violations of g 1 • World data (today) allows a NLO p. QCD fit to the scaling violations in g 1 resulting in the polarized gluon distribution and its first moment. • SM collaboration, B. Adeva et al. PRD (1998) 112002 DG = 1. 0 +/- 1. 0 (stat) +/- 0. 4 (exp. Syst. ) +/- 1. 5 (theory) • Theory uncertainty dominated by the lack of knowledge of the shape of the PDFs in unmeasured low x region where EIC data will play a crucial role. • With approx. 1 week of EIC statistical and theoretical uncertainties can be reduced by a factor of 3 -5 -- coupled to better low x knowledge of spin structure function -- less sensitivity on factorization & re-normalization scale variations in fits as new data at low x is acquired See J. Lichtenstadt’s talk in this meeting December 18, 2002 Physics Opportunities at Future Polarized Colliders 12
Photon Gluon Fusion at EIC Signal: PGF Background QCD Compton December 18, 2002 • “Direct” determination of DG -- Di-Jet events -- High p. T hadrons • High Sqrt(s) at EIC & Pol. HERA -- no theoretical ambiguities in interpretation of data • Both methods tried at HERA in un-polarized gluon determination & both are successful! -- NLO calculations exist -- H 1 and ZEUS results -- Consistent with scaling violation F 2 results on G Physics Opportunities at Future Polarized Colliders 13
G. Radel, A. De Roeck, EIC WS, Yale’ 00 Di-Jet events Analysis at NLO At Electron Ion Collider: 4+ fb-1/yr • • At HERA: 150 pb-1/yr Statistical accuracies shown for at 2 EIC luminosities and 1 pol. HERA luminosity Detector smearing effects considered Analysis performed at next to leading order Will easily differentiate amongst different DG scenarios Uncertainty in the first moment of DG will be improved by factors of 3 J. Lichtenstadt, A. D. & V. Hughes, EIC WS, Yale’ 00 If combined with g 1 NLO analysis effective improvement is even more EIC will give an absolute uncertainty of about 3 -5% in DG December 18, 2002 Physics Opportunities at Future Polarized Colliders 14
G. Radel & A. De Roeck, EIC WS, BNL’ 02 Di-Jet World Data for DG/G EIC Di-Jet DATA 2 fb-1 HERA Di-Jet Data 500 pb-1 EIC: Good precision Constrains shape of DG(x) HERA: Lower x access Polarization in HERA much more difficult than RHIC(? ) D. Barber’s talk tomorrow December 18, 2002 Physics Opportunities at Future Polarized Colliders 15
Polarized PDFs of the Photons • Photo-production studies with single and di-jet Direct Photon Resolved Photon • Photon Gluon Fusion or Gluon Fusion (Photon resolves in to its partonic contents) • Resolved photon asymmetries result in measurements of spin structure of the photon • Asymmetries sensitive to gluon polarization as well… but we will consider the gluon polarization “a known” quantity! December 18, 2002 Physics Opportunities at Future Polarized Colliders 16
M. Stratmann & W. Vogelsang, EIC WS, BNL ‘ 01 PDFs of polarized photon at EIC • Stat. Accuracy estimated for 1 fb-1 running (1 month at EIC including 50% inefficiencies of detector) • Single and double jet asymmetries • ZEUS acceptance Direct Photon • Will resolve photon’s partonic spin contents Resolved Photon December 18, 2002 Physics Opportunities at Future Polarized Colliders 17
M. Stratmann & W. Vogelsang, EIC WS, Yale’ 00 & Pol. HERA WS, DESY’ 99 Photon Structure Function at HERA/EIC 85 pb-1/day December 18, 2002 HERA 150 pb-1/yr Physics Opportunities at Future Polarized Colliders 18
Parity Violating Structure Function g 5 • This is also a test • Experimental signature is a huge asymmetry in detector (neutrino) • Unique measurement • Unpolarized x. F 3 measurements at HERA in progress • Will access heavy quark distribution in polarized DIS December 18, 2002 For HERA & EIC Physics Opportunities at Future Polarized Colliders 19
J. Contreras & A. De Roeck, Pol. HERA WS, DESY’ 99 & EIC WS BNL’ 01 Measurement Accuracy PV g 5 at EIC Assumes: for EIC (LEFT FIGURE) 1. Input GS Pol. PDfs 2. x. F 3 measured by then 3. 2 fb-1 luminosity 4. Makes the case for e+/e- beam facility Assumes for HERA (RIGHT FIGURE) 1. Input GS polarized PDFs 2. x. F 3 is measured by then 3. 1 fb-1 luminosity 4. Both e+/- beams December 18, 2002 Physics Opportunities at Future Polarized Colliders 20
S. Bass, A. De Roeck & A. Deshpande, EIC WS, Yale’ 00 Drell Hern Gerasimov Spin Sum Rule • DHG Sum rule: • Inclusive Photo-production measurement • Using electron tagger in EIC -- Q 2 ~ 10 -6 10 -2 Ge. V 2 -- Sqrt(s) ~ 25 85 Ge. V HERA: -- Q 2 ~ 10 -6 10 -3 Ge. V 2 -- Sqrt(s) ~ 40 250 Ge. V • At EIC n range: Ge. V few Te. V • AT HERA : 10 s of Ge. V 10 s Te. V • Although contribution from to the this sum rule is small, the high n behavior is completely unknown and hence theoretically biased in any present measurements at: Jefferson Lab. , MAMI, BNL December 18, 2002 Physics Opportunities at Future Polarized Colliders 21
S. Bass & A. De Roeck DGH Spin Sum Rule Contribution from EIC/e. RHIC and HERA (1)+(2) =0. 5 (1)+(4) (1)+(2) =-0. 5 (1)+(3) December 18, 2002 Physics Opportunities at Future Polarized Colliders 22
HERA, TESLA-N, ELFE E. Kinney & U. Stoesslein, EPIC WS, MIT’ 01 Strange Quark Distributions at EIC • After measuring u & d quark polarized distributions…. Turn to s quark (polarized & otherwise) • Detector with good Particle ID: pion/kaon separation • Upper Left: statistical errors for kaon related asymmetries shown with A 1 inclusive • Left: Accuracy of strange quark distribution function measurements possible with EIC and HERMES (2003 -05) and some theoretical curves on expectations. December 18, 2002 Physics Opportunities at Future Polarized Colliders 23
M. G. Perdekamp, EIC WS, Yale’ 00 TESLA-N, ELFE in HERMES Kinematics Transversity EIC with 80 pb-1~ 1 day • Measure helicity flip amplitude = d(x, Q 2) quark transversity • Does not mix with gluon distributions in its QCD evolution • Measure single spin asymmetries (DIS + p 0) • Large acceptance desired |eta|<3. 5 Collins/fragmentation function being measured by: RBRC from e+e- at B-factor at BELLE Expect preliminary results in ’ 03 December 18, 2002 Physics Opportunities at Future Polarized Colliders 24
ELFE EIC DVCS/Vector Meson Production • Hard Exclusive DIS process • g (default) but also vector mesons possible • Remove a parton & put another back in! Microsurgery of Baryons! • Claim: Possible access to skewed or off forward PDFs? Polarized structure: Access to quark orbital angular momentum? On going theoretical debate… experimental effort just beginning at HERA, Jlab… For ELFE this is the principle motivation December 18, 2002 Physics Opportunities at Future Polarized Colliders 25
A. Sandacz, EIC WS, BNL’ 02 D. Hassel, R. Milner Deeply Virtual Compton Scattering DVCS has already been seen at HERA… New Detector Techniques at EIC Roman pots a la PP 2 PP at RHIC DVCS study for EIC (preliminary) Q 2> 1 Ge. V 2 20<W<95 Ge. V 0. 1<|t|<1. 0 Ge. V 2 December 18, 2002 10 x 250 Ge. V Full curve: all events Dashed curve: accepted events Q 2>1 Ge. V 2: 50 K events/fb-1 Physics Opportunities at Future Polarized Colliders 26
W. -D. Nowak, Int. WS on Hadron Structure, Trieste, Feb. 2002 Future Fixed Target DIS at DESY • TESLA-N ----- Use one (positron) arm of TESLA for polarized fixed target experiment Beam energy variable 30 -250 Ge. V Large Q 2 range compared to present fixed target experiments PHYSICS: Transversity distributions, Polarized Gluon Distribution • Run in parallel with the ee collider experiments • Will need: 1. Polarized source and injector 2. Experimental hall and short tunnel 3. Beam dump Detector design considerations: • Size comparable to COMPASS at CERN • Good momentum resolution • Good PID RICH, TRD as well as EMCalorimetry December 18, 2002 Physics Opportunities at Future Polarized Colliders 27
W. -D. Nowak, Int. WS on Hadron Structure, Trieste, Feb. 2002 R. Kaiser & D. Ryckbosch, private comm. , SPIN 2002 at BNL ELFE at DESY • ELEF at DESY: -- Inject electron beam at 30 Ge. V in modified HERA-e -- Use HERA as stretcher ring extract high duty factor -- Measurement goal: Exclusive reactions with high precision -- PHYSICS: Skewed parton distributions Orbital angular momenta December 18, 2002 Physics Opportunities at Future Polarized Colliders 28
Towards EIC at BNL…. • September 2001: EIC grew out of joining of two communities: 1) polarized e. RHIC (ep and e. A at RHIC) 10 Ge. V e X 250 Ge. V p or 100 Ge. V A BNL, UCLA, YALE and people from DESY & CERN 2) Electron Poliarized Ion Collider (EPIC) 3 -5 Ge. V e X 30 -50 Ge. V polarized light ions Colorado, IUCF, MIT/Bates, HERMES collaborators EPIC + e. RHIC = “EIC” • February 2002: White paper submitted to NSAC Long Range Planning Review Received enthusiastic support as a next R&D project (see: Do. E Webpage for Nuclear Physics Long Range Planning) • Steering Committee: 7 members, one each from BNL, IUCF, LANL, LBL, MIT, UIUC, Yale + Contact person (AD) • ~20 (~13 US + ~7 non-US) Institutes, ~100 physicists + ~40 accelerator physicists • See for more details: EIC Web-page at “http: //www. bnl. gov/eic” • Annual Meetings: MIT Sep. ’ 01, BNL Feb. ’ 02, BNL(? ) May/June’ 03 • Subgroups: Accelerator WG, Physics WG, Detector WG December 18, 2002 Physics Opportunities at Future Polarized Colliders 29
EIC Layout (present status) 2 Ge. V (5 Ge. V) e 2 -10 Ge. V EMPTY IP 12 PHOBOS IP 10 p IP 2 BRAHMS PP 2 PP RHIC IP 8 PHENIX IP 4 CAD/RF EMPTY • • • Proposed by BINP & MIT/Bates E-ring is ¼ of RHIC ring Collisions in ONE interaction region Collision energies 5 -10 Ge. V Injection linac 2 -5 Ge. V Lattice based on “superbend” magnets • Self polarization using Sokolov Ternov Effect: (14 -16 min pol. Time) • IP 12, IP 2 and IP 4 are possible candidates for collision points IP 6 STAR December 18, 2002 OTHER : Ring with 6 IPS (Yale’ 00), Linac-Ring (Yale’ 00), Linac-Re-circulating ring (BNL’ 01) Physics Opportunities at Future Polarized Colliders 30
A Detector for EIC A “ 4 p” Detector • Scattered electrons to measure kinematics of DIS • Scattered electrons at small (~zero degrees) to tag photo production • Central hadronic final state for kinematics, jet measurements, quark flavor tagging, fragmentation studies, particle ID • Central hard photon and particle/vector detection (DVCS) • ~Zero angle photon measurement to control radiative corrections and in e-A physics to tag nuclear de-excitations • Missing ET for neutrino final states (W decays) • Forward tagging for 1) nuclear fragments, 2) diffractive physics • DETECTOR DEVELOPMENT JUST BEGINNING: Invitation to Join! -- Some early effort (W. Krasny & J. Chwastowski, Yale 00 WS) -- New effort for modified EIC ring lattice to begin BNL/MIT/UIUC/+YOU! • EIC will provide: 1) Variable beam energies 2) different hadronic species, some of them polarized, 3) high luminosity December 18, 2002 Physics Opportunities at Future Polarized Colliders 31
A time line for EIC… “Predictions are very difficult to make, especially when they are about the future” --- Albert E. • • • Proposal by 2004 -2005 Expected formal approval 2005 -6 Long Range Review R&D money could start for hardware 2007 Construction of IR and Detector begin 2007 -2008 3 -5 years for staged detector and IR construction without interfering with the RHIC running • First collisions (2010 -2011)? ? ? If any one knows how to do this earlier… -- I am listening. December 18, 2002 Physics Opportunities at Future Polarized Colliders 32
RHIC Accelerator Complex RHIC p. C Polarimeters BRAHMS & PP 2 PP (p) Absolute Polarimeter (H jet) PHENIX (p) STAR (p) Spin Rotators Partial Siberian Snake LINAC BOOSTER Pol. Proton Source 500 m. A, 300 ms Siberian Snakes 2 1011 Pol. Protons / Bunch e = 20 p mm mrad AGS 200 Me. V Polarimeter AGS Internal Polarimeter Rf Dipoles RHIC accelerates heavy ions to 100 Ge. V/A and polarized protons to 250 Ge. V December 18, 2002 Physics Opportunities at Future Polarized Colliders 33
E 950 Experiment at AGS (1999) RHIC Polarimetry Now Carbon filament target (5 mg/cm 2) in the RHIC beam Measure recoil carbon ions at q~90º 100 ke. V < Ecarbon< 1 Me. V Wave-Form Digitizer +FPGA high counting rates (~0. 5 MHz) scaler measurement d. A ~ 3 10 -4 in ~1 minute. Arrival time (ns) RHIC Polarimetry up Si #6 left Si #5 Si #4 Si #1 Carbon Si #2 Si #3 down ADC values Beam’s View BNL, Kyoto, RBRC, RIKEN, Yale December 18, 2002 Physics Opportunities at Future Polarized Colliders 34 righ
BNL, RBRC, RIKEN Siberian Snakes Effect of depolarizing resonances averaged out by rotating spin by large angles on each turn RHIC PHENIX STAR 4 helical dipoles S. snake 2 snakes in each ring -- axes orthogonal to each other December 18, 2002 LINAC Physics Opportunities at Future Polarized Colliders AGS 35
Blue Ring, Run 1 (2000 -2001) Successful Operation of the Snake • Injection with Spin Flipped: Asymmetry Flipped • Adiabatically Snake on: Horizontal polarization • Accelerate equivalent to 180 o rotation: 180 o rotated Successful Single Snake Operation ! December 18, 2002 Physics Opportunities at Future Polarized Colliders 36
Polarization in Run 2 (January 2002) Yellow Ring December 18, 2002 Blue Ring Physics Opportunities at Future Polarized Colliders 37
Why low polarization? AGS! PRHIC Source Improvement New AGS SNAKE 2004 -5 Ramp up Spead Injection 1 st Year 10% 20% 30% PAGS power generator failure ½ ramp up speed 2 x resonance effect December 18, 2002 Physics Opportunities at Future Polarized Colliders 38
Machine Performance Expectations RUN #proton/ bunch #bunch [x 109] Beta* (m) Emittanc e (pmm) Luminosity 1030 cm-2 s-1 Pol. (%) 20012002 70 55 3 25 1. 8 15 -25 20022003 2005 - 100 112 1 25 16 45 -55 ? 112 1 ? ? 70 -80 200 112 1 20 80 70 Design December 18, 2002 Physics Opportunities at Future Polarized Colliders 39
A Case for Polarized Colliders: Excellent! • The polarized EIC and HERA for e-N scattering will enable the polarized DIS studies of nucleons in a completely new x-Q 2 -- A robust physics program exists with pros and cons w. r. t. high luminosity of EIC and higher CM energy of HERA • If we are lucky: HERA II finds Physics Beyond SM, polarized HERA will be imperative to understand the chiral properties of the object(!) -- Polarized THERA program will be concentrated around this… • Physics with variable Sqrt(s) at EIC will include in addition: -- inclusive physics in DIS as well as photo-production regime -- semi-inclusive physics with good particle ID -- exclusive physics leading to DVCS, DES and further to GPDs -- study of evolution of any of the pdfs when necessary • Proof of high energy polarized proton beam is at hand with RHIC Spin • Primary physics program for TESLA-N/ELFE will limit itself to already explored x -Q 2 coverage, but with significantly enhance statistical accuracy with huge luminosities hence allowing detailed studies of exclusive reactions, possibly leading to angular momenta in q and g December 18, 2002 Physics Opportunities at Future Polarized Colliders 40
Some spin & Low x/High Q 2 surprises… • • Stern & Gehrlach (1921) Space quantization associated with direction Goudschmidt & Ulhenbeck (1926): Atomic fine structure & electron spin magnetic moment Stern (1933) Proton anomalous magnetic moment 2. 79 m. N Kusch(1947) Electron anomalous magnetic moment 1. 00119 m 0 Prescott & Yale-SLAC Collaboration (1978) EW interference in polarized e -d DIS, parity non-conservation European Muon Collaboration (1989) Spin Crisis/Puzzle E 704, AGS pp scattering, HERMES (1990 s) Transverse spin asymmetries (? ? ) RHIC Spin (2001) Transverse spin asymmetries (? ? ) December 18, 2002 • Elastic e-p scattering SLAC (1950 s) Q 2 ~ 1 Ge. V 2 Finite size of the proton • Inelastic e-p scattering SLAC (1960 s) Q 2 > 1 Ge. V 2 Parton structure of the proton • Inelastic m-p scattering off p/d/N at CERN (1980 s) Q 2 > 1 Ge. V 2 Unpolarized EMC effect, nuclear shadowing? • Inelastic e-p scattering at HERA/DESY (1990 s) Q 2 > 1 Ge. V 2 Unexpected rise of F 2 at low x Diffraction in e-p Saturation(? ? ) Physics Opportunities at Future Polarized Colliders 41
Thanks…. . • Many people were listed along with their work for various polarized HERA and Electron Ion Collider Workshops…. -- Many more participated but can not be mentioned…. • TESLA-N, ELFE : W. D. Nowak, R. Kaiser, D. Ryckbosch • EIC Accelerator Issues: V. Ptytsin and the EIC Accelerator group (BNL/MIT-Bates) • Initial versions of some transparencies shown in this talk were prepared with A. De Roeck(CERN) for previous workshops and presentations for polarized HERA and making the case for EIC December 18, 2002 Physics Opportunities at Future Polarized Colliders 42
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