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1 Online Evaluation der Lehrveranstaltung Preis: Netbook, 2. Preis: Buchgutschein über 00,- EUR, 3. Preis: Buchgutschein über 50,- EUR. Bitte informieren Sie Ihre Studierenden bei der Ausgabe der Zugangsdaten über die Verlosung und weisen Sie insbesondere auf folgende Bedingungen hin: die Gewinne können nur nach Vorlage der Originalzugangsdaten und einer Immatrikulationsbescheinigung vergeben werden. Promotionsstudierende sind von der Verlosung ausgeschlossen.

2 Einführung (Jim Formfaktoren (Jim) (skipped...) DIS (Jim) Scaling (Tobias) Spin Structure (Tobias) SumRules/Gluons (Jim) had. Massen (Tobias) chiral sym. (Jim) (2 talks 4:00-5:30) 5:30) Antiprotonen (Tobias) ccbar/exotic (Tobias) New States (Jim) (3 talks 4:00-6:5) Pbar FF (Jim) (2 talks 4:00-5:30) TBA (Tobias)

3 Seminar talks Title Speaker Date contact PANDA Katrin B TS arxiv v BES-III Julien P TS arxiv v Jlab 2 GeV GlueX Tobias T JR proposal COMPASS hadron program Sonja K 8.2. JR Rare eta-meson decays Malte A 29.0 TS WASA@COSY // MAMI // ELSA Hadron mass formulas Bartholomaeus K 8.2. JR CLEO Patrik Z 29.0 TS

4 Review (I) Review (I) Heavy Nuclear Targets Shadowing EMC Effect Sokolov Turrnov Effect to polarize electron beams HERMES (storage cell) Nucleon Spin Dependent Structure Functions Gribov-Lipatov- Altarelli-Parisi equations SMC Experiment, polarized muon beam Dynamic Nuclear Polarization

5 Frozen Spin Target Nucleon relaxation time: T n ~ /Temperature This characterizes the polarization decay if the polarizing mechanism (microwaves) is turned off. Typical: T n n( (K) ~ minutes T n (0.5K) ~ hours T n n( (<0.K) ~ days Typical operation is with mk and a T holding field.

6 Two Operation Schemes Continuous mode: i.e. max. nucleon polarization by continuous microwave pumping of electron spins Frozen spin mode: i.e. without microwave pumping, thus the nucleon polarization decreases slowly Procedure:. Polarize DNP at high field B~2.5-5 Tesla, T=300 mk 2. Stop microwave pumping at maximum nucleon polarization (temperature lowers to T=50-60 mk) 3. Change to holding field B= Tesla mechanical movements 4. Data taking

7 Comparison. Continuous mode + Highest K & 5T (e.g. SLAC) L=0 35 / cm 2 s + Highest polarization (50 mk & 2.5 T) P p = 92%; P D =55% (e.g. SMC, COMPASS) - Limited particle detection due to mag. coils etc. 2. Frozen spin mode + Larger solid angle for particle detection + Outgoing charged particles are less effected dby the reduced magnetic field - Lower luminosity it (L~0 30 / cm 2 s) - Relaxed polarization <P> = 0.8 P max

8 Muon Spectrometer The spectrometer includes hodoscopes, polarized target, proportional wire chambers, dipole magnet (4.4 Tm), drift chambers, calorimeter, streamer tubes, drift tubes and a 2m iron absorber.

9 Kinematic Coverage & Data-Taking During the 993 run (34 days beam on target).7x0 7 DIS events from.6x0 0 3 muons. (kinematic range) (target vertex)

10 Proton Asymmetries Longitudinally polarized target transverse polarization

11 P and N Structure Functions Other experiments use a 3 He target to measure the neutron directly, because the protons have opposite spin. Systematic ti errors Note: the ratio g p /g n ~ - at low x, in contrast to F 2p /F 2n ~! p n g g = ( Δu ( x ) Δ d ( x ) + 2 Δu ( x ) 2 Δ d ( x ) ) 6 V V Thus, either valence quarks dominate, or Δu(x) Δd(x)!

12 First Moment of g p The determination of the first moment requires an extrapolation over the full x range. The data show a clear violation of the Ellis-Jaffe sum rule. The band shows the uncertainty from F/D.

13 First Moment of g n

14 Test of Bjorken Sum Rule The measured p and D first moments (and thus also of the neutron) agree with the Bjorken sum rule, but not with Ellis-Jaffe. Jff

15 Quark Contribution to the Spin The Ellis-Jaffe Jff sum rule assumed dδs=0, 0if we relax this condition, but still assume ΔG=0 and SU(3) symmetry, then ΔΣ~0.22, 022 Δu~0.8, 08 Δd~-0.46, 046 and dδs~

16 How Valid is Δu(x)=Δd(x) Δd(x)? We have seen that the ratio g p /g n ~ - at low x, in contrast to F p n 2p /F 2 ~! p n g g = { Δu ( x) Δd ( x) + 2Δu ( x) 2Δd ( x) } 6 V Since we think the sea dominates at low x, it appears as if Δu(x) Δd(x). To address this question, let us first look at the Gottfried sum rule: S G = p n ( F F ) dx x = u ( x) d ( x) V [ ] [ ] dx + u ( x) d ( x) 2 2 V V if u(x)=d(x) then S G =/3 is in disagreement with the data from NMC (CERN ), which after extrapolation down to x=0 and up to x= is: S G =0.235± This either means u(x) d(x) in the proton, or u p(x) d n(x). It is assumed that the isospin symmetry of proton&neutron is however conserved. 2 Methods to find out: Drell-Yan and semi-inclusive DIS dx

17 Parton Distributions from Drell-Yan The Drell-Yan process (qq l + l - ) can provide excellent discrimination between isospin symmetric and nonsymmetric sea parton distributions. Considering only q V q S interactions we have: pp σ 4u pn σ uv and thus A DY = V ( x) u ( x) + dv ( x) d ( x) ( x ) d ( x ) + d ( x ) u ( x ) σ σ pp pp σ + σ pn V = ( 4λV )( λs ) + ( λv )( 4λs ) ( 4 λ + )( λ + ) + ( λ + )( 4 λ + ) pn + V s V s where λ V (x)=u V (x)/d V (x) and λ s (x)=u(x)/d(x)

18 Drell-Yan Measurements with ihna5 They used 0 9 protons/s at 450 GeV from SPS and measured muon pairs in the NA0 spectrometer m hadron absorber, b toroid magnet t2x4 4MWPCs and hodoscopes, 20 cm long LH 2 target.

19 Dilepton Spectrum After integrating the data an asymmetry of A DY =-0.09±0.02±0.025 DY is measured. From this they determine (x=0.8) λ s =0.5±0.04±0.05 Suggesting that isospin symmetry is indeed violated in the light quark sea of the nucleon.

20 Flavor Asymmetry of the Light Quark Sea in Semi-Inclusive DIS The ratio (d-u)/(u-d) is determined dfrom the relative π ± yields from p and n targets. r ( x z ) N N ( x, z) N π n ( x z) π ( x, z) N ( x, z) π p,, = + + π p where z=e π /ν is the fraction of the γ* energy carried by the pion. n

21 Fragmentation Functions The fragmentation functions D qπ (z) give the probability that a quark fragments to a given pion: N ± { } ( ± ± π π x, z) e q ( x) D ( z) + q ( x) D ( z ) π 2 i i i Assuming isospin i symmetry between the proton and neutron and C invariance, we are left with only 2, a favored and a disfavored dfragmentation ti functions D π+ u, D π- u q i i q i

22 Semi-Inclusive DIS The previous equations can be combined to isolate a quantity sensitive to the flavor asymmetry: where ( x) u ( x) J ( z) [ r( x, z) ] [ r( x, z) ] = ( x ) u ( x ) J ( z ) [ r ( x, z ) ] + [ r ( x z ) ] d d, J ( z) 3 + = 5 D D ( z) ( z ) and D π π + ( z) = D ( z) D ( z) The previous assumptions imply that the top equation does not tdepend dupon z. u u

23 HERMES has measured semi-inclusive DIS and their results are indeed independent on z Independence on z

24 Asymmetry of the Light Quark Sea After averaging over z, the HERMES results show an excess of d over u. The E866 data (Fermilab) are from Drell- Yan and parameterize u+d to extract u-d from their ratio u/d. Their results show that the sea asymmetry is consistent for both methods even though the Q 2 range is a factor 20 different. The integral accounts for 2/3 of the Gottfried sum rule deficit.

25 Bjorken Sum Rule One of the most fundamental sum rules and a cornerstone of the quark-parton model is the Bjorken sum rule. This relates the difference of the proton and neutron Γ values to g A/g V, the ratio of the axial to vector weak coupling constant from neutron β-decay. p n g A Γ Γ = = 6 g V 0.20() This equation is only rigorously true in the infinite momentum frame. At Q 2 =0 GeV 2, the difference becomes 0.87(3) including 3 rd order corrections in α s.

26 Ellis-Jaffe Sum Rule If one assumes exact SU(3) symmetry and Δs=0, then Γ p g 5 3 / A F D = + = 2 g V 3 F / D (3) F/D=0.575(6) are the coefficients from semileptonic hyperon decay. Radiative corrections modify this to 0.70(5) at Q 2 =0GeV 2. The EMC data show that Γ p is smaller than this prediction, which in the quark-parton model implies that ΔΣ (contribution of quark spins to the proton spin) is small. This result was called the SPIN crisis and is at the origin of the current interest in polarized DIS.

27 Gross-Llewellyn Smith Sum Rule The GLS sum rule is the most accurately tested sum rule. It predicts the number of valence quarks in a nucleon, up to higher order corrections, and uses νn results xf 3. In the QPM, the GLS sum rule is: S GLS ν N xf3 dx = U U + D = ( ) ( ) 3 = D 2x 0 The value from the CCFR collaboration (Fermilab) is S GLS =2.50±0.08± Using the value Λ=23 ± 50 MeV from the Q 2 evolution of the SF, the theoretical prediction is S GLS =2.66±0.04.

28 Alder Sum Rule The Alder sum rule predicts the difference between the νn and νp SFs. S A ( νn νp ) F F 2 2 dx = d ( x) + u ( x) d ( x) ( ) 2 n n p u p x x 0 0 = = = ( D + U ) ( D + U ) n n ( U U ) + ( D D ) = p p Assuming that the Callan-Gross relation hold, the WA25 collaboration (CERN 984/85) measured: S A =.08 ± 0.08 ± 0.8 To improve the 20% error one needs a light Z target, t but then the cross section is too low. dx