Detector integration @HERMES Delia Hasch outline: physics goals & experimental design – a brief history physics achievements & lessons from HERMES – a few examples Common ENC/EIC workshop at GSI, Darmstadt, Germany, 28-20 May 2009

HERMES: physics scope Technical Design Report July 1993 spin puzzle EMC 1988: DS=0.12±0.17

HERMES: physics scope  inclusive & semi-inclusive DIS Technical Design Report July 1993  inclusive & semi-inclusive DIS - g1 and g2 the proton and neutron - tensor structure fct - flavour dependence of quark helicity distribution EMC 1988: DS=0.12±0.17 - dV/uV from F2n/F2p - sea quark distributions

HERMES: physics scope  inclusive & semi-inclusive DIS Technical Design Report July 1993  inclusive & semi-inclusive DIS - g1 and g2 the proton and neutron - tensor structure fct - flavour dependence of quark helicity distribution - dV/uV from F2n/F2p - sea quark distributions EMC 1988: DS=0.12±0.17 polarised high energy lepton beam polarised proton and neutron targets spectrometer with good PID

HERMES: choice of technologies polarised high energy lepton beam polarised proton and neutron targets spectrometer with good PID  statistical precision: f: target dilution factor f=1 gas targets f~0.02 solid targets

HERMES: choice of technologies polarised high energy lepton beam polarised proton and neutron targets spectrometer with good PID  statistical precision: novel technologies:  gas target in a storage cell f=1 rapid polarisation reversal very thin exit window f: target dilution factor f=1 gas targets f~0.02 solid targets  polarised e- or e+ of HERA storage ring fast polarisation build up (~30’) polarisation reversal

HERMES: choice of technologies lepton polarisation at HERA <Pb>~45-55%

HERMES: choice of technologies HERMES integration

HERMES: choice of technologies HERMES integration target section: beam live time requirement: ~45h upper limit for target density: 1015 atoms/cm2

HERMES: choice of technologies spectrometer P (GeV) cumulative rate (s-1sr-1GeV-1) p clear identification of electrons for DIS event ID: (large p bg from g-production) calorimeter + TRD: HRF~103 e

HERMES: choice of technologies spectrometer particle ID: lepton ID with e ~ 98%, hadron contamination <1% RICH: p, K, p ID within 2<Eh<15 GeV (p from 1 GeV) resolution: dp/p ~ 1.5%, dq < 0.6 mrad (slightly worse with RICH)

HERMES angular acceptance effect of septum plate polar angle azimuthal angle

physics scope & achievements inclusive & semi-inclusive DIS - g1 and g2 the proton and neutron - tensor structure fct - flavour dependence of quark helicity distribution - dV/uV from F2n/F2p - sea quark distributions inclusive & semi-incl. & exclusive DIS - g1 for p, n and d - tensor structure fct first 5-flavour separation of Dq, Ds first gluon polarisation - first SSA in sidis: AUL , AUT first DVCS with polarised beam/target and two lepton charges flavour asymmetry of light sea hadron multiplicities - nuclear effects in incl.+semi-incl. DIS - exclusive VM production, polarised SDMEs - exclusive 1 and 2 pion production lambda polarisation exotic states …

- GPD&TMD physics program - lessons from HERMES - GPD&TMD physics program - ~ hermetic spectrometer  full event reconstruction  full kinematic coverage good e/h separation & hadron ID over whole momentum range lumi determination for measurement of absolute cross section (differences) both lepton beam charges desirable

lesson 1: full event reconstruction example: deeply virtual Compton scattering & GPDs

lesson 1: full event reconstruction example: deeply virtual Compton scattering & GPDs HERMES till 2005 g e+, p e-, e

exclusivity via missing mass 3% ‘exclusive sample’  BH&DVCS + intermediate nucleon resonance production

1 out of 17 DVCS observables  model independent extraction of CFF HIm, HRe [M. Guidal, H. Moutarde,0905.1220] fraction of associated  full event reconstruction with recoil @HERMES 2006/07

HERMES06/07 with recoil

HERMES06/07 with recoil D production full event reconstr., PID capabilities: ID of intermediate D production

lesson 1&2: full kinematic coverage & PID example-I : semi-inclusive 2 hadron production: transversity from IFF incomplete angular coverage restricted momentum range for PID example-II : semi-inclusive 1 hadron production: transversity&friends incomplete pT coverage

2-hadron production: only relative momentum of hadron pair relevant lesson 1&2: example-I 2-hadron production: interference fragmentation function between pions in s-wave and p-wave only relative momentum of hadron pair relevant !collinear factorisation!  relativ. momentum: R=(Pp++Pp-)/2  can have transv. component even when integrating over PT of the pair  integration over transverse momentum of hadron pair simplifies factorisation (collinear!) and Q2 evolution however cross section becomes very complicated (depends on 9! variables)  sensitive to detector acceptance effects

(1)2-hadron production (f) - inclompete angular coverage - lesson 1&2: example-I (1)2-hadron production [thesis P. van der Nat, Vrije Universiteit Amsterdam 2007] - inclompete angular coverage - (f)

(1)2-hadron production (f) - inclompete angular coverage - lesson 1&2: example-I (1)2-hadron production [thesis P. van der Nat, Vrije Universiteit Amsterdam 2007] - inclompete angular coverage - (f) resolve acceptance effects: … and preferably even more kinematic variables

2-hadron production - restricted momentum range - lesson 1&2: example-I [thesis P. van der Nat, Vrije Universiteit Amsterdam 2007] 2-hadron production - restricted momentum range - …facilitate interpretation q integration

2-hadron production q acceptance is momentum dependent: lesson 1&2: example-I [thesis P. van der Nat, Vrije Universiteit Amsterdam 2007] 2-hadron production - restricted momentum range - …facilitate interpretation q integration q acceptance is momentum dependent: full acceptance

2-hadron production q acceptance is momentum dependent: lesson 1&2: example-I [thesis P. van der Nat, Vrije Universiteit Amsterdam 2007] 2-hadron production - restricted momentum range - …facilitate interpretation q integration q acceptance is momentum dependent: full acceptance

2-hadron production - restricted momentum range - binning also in q lesson 1&2: example-I [thesis P. van der Nat, Vrije Universiteit Amsterdam 2007] 2-hadron production - restricted momentum range - binning also in q

lesson 1&2: full kinematic coverage & PID example-I : semi-inclusive 2 hadron production: transversity from IFF incomplete angular coverage: need to evaluate AUT instead of sUT  complicates interpretation restricted momentum range for PID need to fit also polar angular dependence  highly non-linear fits

lesson 1&2: example-II 1-hadron production: Collins effect:

1-hadron production: Collins effect: lesson 1&2: example-II 1-hadron production: Collins effect: convolution integral over initial (pT) and final (kT) quark transverse momenta for a model independent extraction: evaluate PhT weighted asymmetries  product of dqH1 instead of convolution integral

lesson 1&2: example-II [L. Pappalardo, PhD Thesis University Ferrara] acceptance studies: Monte Carlo: gmc_trans: generator for transversity + TMDs simulates full kinematic dependences of observables Collins asymmetries unweighted

lesson 1&2: example-II [L. Pappalardo, PhD Thesis University Ferrara] acceptance studies: Monte Carlo: gmc_trans: generator for transversity + TMDs simulates full kinematic dependences of observables Collins asymmetries weighted  large acceptance effects

pT weighted asymmetries: lesson 1&2: example-II [U. Elschenbroich, PhD Thesis University Erlangen] pT weighted asymmetries: acceptance depends strongly on pT: MC distributions: p+/- p0

lesson 1&2: full kinematic coverage & PID example-II : semi-inclusive 1 hadron production: transversity&friends incomplete pT coverage: pT dependent acceptance biases asymmetry extraction ( way out: multi-D unfolding )

lesson 1&2: full kinematic coverage & PID example-II : semi-inclusive 1 hadron production: transversity&friends incomplete pT coverage: pT dependent acceptance biases asymmetry extraction ( way out: multi-D unfolding ) BUT “no particle physics experiment has a perfect acceptance”

lesson 1&2: full kinematic coverage & PID example-II : semi-inclusive 1 hadron production: transversity&friends incomplete pT coverage: pT dependent acceptance biases asymmetry extraction ( way out: multi-D unfolding ) BUT “no particle physics experiment has a perfect acceptance”

lesson 1&2: full kinematic coverage & PID example-II : semi-inclusive 1 hadron production: transversity&friends incomplete pT coverage: pT dependent acceptance biases asymmetry extraction ( way out: multi-D unfolding ) BUT “no particle physics experiment has a perfect acceptance”  need the tools (Monte Carlo) to estimate detector effects  need the tools (e.g. multi-D unfolding) to correct for

lesson 3: lumi  cross section (differences) Lesson from RHIC: measure cross sections for particle production justify validity of pQCD interpretation of you data  measure your hadron multiplicities (or better prod. cross section) for ‘own’ (spin-independent) fragmentation fct.s  get rid of interpretation uncertainties due to denominator in asymmetries example-I: lepton-beam or virtual-photon asymmetries AUT example-II: DVCS asymmetries

interpretation uncertainties I lesson 3: example-I interpretation uncertainties I SIDIS AUT: lepton-beam or virtual-photon asymmetries Collins asymmetry:  account for A(x,y) and B(y) to get virtual-photon asymmetries BUT: need RSIDIS this is an issue @EIC/ENC !

interpretation uncertainties II lesson 3: example-II interpretation uncertainties II DVCS: e.g. beam-charge asymmetry … wanted: interference term gets admixture of Fourier coefficients related to BH and DVCS squared terms  need to be accounted for in fitting procedure

lesson 4: both lepton beam charges desirable

lesson 4: both lepton beam charges desirable DVCS: charge asymmetry CFF Re (GPDs) contribution of ‘D-term’

lesson 4: both lepton beam charges desirable DVCS: charge asymmetry & separation of interference and DVCS squared terms CFF Re (GPDs) contribution of ‘D-term’

the end of the story ? 1/7/07@ 1:09:56 am T

the end of the story ? 1/7/07@ 1:09:56 am T more to come: EIC/ENC

conclusion  lessons from HERMES many pioneering measurements ~ hermetic spectrometer  full event reconstruction  full kinematic coverage good e/h separation & hadron ID over whole momentum range lumi determination for measurement of absolute cross section (differences) both lepton beam charges desirable

backup slides

HERA fills and bunch structure typical beam history for HERA p and e beams: Typical fill~15h (electron scale absent), ‘end of run’ HD  lifetime: 15h  2h high density ‘end of fill run’ beam live time: ~15  2h allowed target densities up to 1017 atoms/cm2

HERA fills and bunch structure Typical fill~15h (electron scale absent), ‘end of run’ HD  lifetime: 15h  2h

good particle ID identify DIS events: HERMES P (GeV) cumulative rate (s-1sr-1GeV-1) identify DIS events: good e/h separation over wide momentum range and espec. at low momenta most modern PID: ALICE: P ~ (0.5 – 100) GeV