Measurements of the QED structure of the photon based on the reaction ee -->
ee \gamma(*)(P^2)\gamma*(Q^2) --> ee mumu are discussed.
  This review is an update of the discussion of the results on the QED
structure of the photon presented in Refs.[1], and covers the published
measurements of the photon structure functions F_2, F_A nd F_B and of the
differential cross-section dsig/dx for the exchange of two virtual photons.Comment: Invited talk given at the 7th International Workshop on Deep
  Inelastic Scattering and QCD, April 19 to 23, 1999, Zeuthen, to appear in the
  proceedings. 8pages 4 figure

Bemelman, W.A.

Endert, E.

Koopmans, R-P.

Moeniralam, H.S.

Romijn, J.A.

Sauerwein, H.P.

English

arXiv

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The decrease in nonsplenic interleukin-6 (IL-6) production after splenectomy indicates the existence of a psoitive feedback loop of IL-6 production during endotixemia in dogs

International Migration, Integration and Social Cohesion online publications

Crossref

Measurements of the QED structure of the photon based on the reaction ee --> ee \gamma(*)(P^2)\gamma*(Q^2) --> ee mumu are discussed. This review is an update of the discussion of the results on the QED structure of the photon presented in Refs.[1], and covers the published measurements of the photon structure functions F_2, F_A nd F_B and of the differential cross-section dsig/dx for the exchange of two virtual photons.Measurements of the QED structure of the photon based on the reaction ee --> ee \gamma(*)(P^2)\gamma*(Q^2) --> ee mumu are discussed. This review is an update of the discussion of the results on the QED structure of the photon presented in Refs.[1], and covers the published measurements of the photon structure functions F_2, F_A nd F_B and of the differential cross-section dsig/dx for the exchange of two virtual photons.Measurements of the QED structure of the photon based on the reaction ee --> ee \gamma(*)(P^2)\gamma*(Q^2) --> ee mumu are discussed. This review is an update of the discussion of the results on the QED structure of the photon presented in Refs.[1], and covers the published measurements of the photon structure functions F_2, F_A nd F_B and of the differential cross-section dsig/dx for the exchange of two virtual photons.Measurementsof the QED structure of the photon based on the reaction ee → ee γ (∗) (P 2 )γ ∗ (Q 2 ) → ee μμ are discussed. This review is an update of the discussion of the results on the QED structure of the photon presented in Refs. [1], and covers the published measurements of the photon structure functions F 2 γ , F A γ and F B γ and of the differential cross-section dσ dx for the exchange of two virtual photons.Measurements of the QED structure of the photon based on the reaction ee --> ee \gamma(*)(P^2)\gamma*(Q^2) --> ee mumu are discussed. This review is an update of the discussion of the results on the QED structure of the photon presented in Refs.[1], and covers the published measurements of the photon structure functions F_2, F_A nd F_B and of the differential cross-section dsig/dx for the exchange of two virtual photons

Nisius, Richard

CERN Document Server

The QED Structure of thePhotonRichard Nisius, on behalf of the LEP Collaborations1CERN, CH-1211 Gene`ve 23, SwitzerlandAbstractMeasurements of the QED structure of the photon based on the re-action ee → eeγ(?)(P 2)γ?(Q2) → ee are discussed. This review is anupdate of the discussion of the results on the QED structure of the photonpresented in Refs. [1], and covers the published measurements of the pho-ton structure functions F γ2 , FγA and FγB and of the differential cross-sectiond=dx for the exchange of two virtual photons.1 IntroductionSeveral measurements concerning the QED structure of the photon have beenperformed by various experiments. Prior to LEP, mainly the structure functionF γ2 of the quasi-real photon, γ, as a function of the photon virtuality Q2 of thevirtual photon, γ?, was measured. The LEP experiments rened the analysisof the  nal state, and derived more information on the QED structure ofthe photon. The interest in the investigation of the QED structure of the pho-ton is twofold. Firstly the investigations serve as tests of QED to O(4), butsecondly, and also very important, the investigations are used to rene the ex-perimentalists tools in a real but clean experimental environment to investigatethe possibilities of extracting similar information from the much more complexhadronic nal state.2 The photon structure function F γ2The structure function F γ2 has been measured using data in the Q2 range fromabout 0.14 up to 400 GeV2. Results were published by the CELLO [2], DEL-PHI [3], L3 [4], OPAL [5], PLUTO [6] and TPC/2γ [7] experiments. Specialcare has to be taken when comparing the experimental results to the QED pre-dictions, because slightly dierent quantities are derived by the experiments.Some of the experiments express their result as an average structure function,hF γ2 (x; Q2)i, measured within their experimental acceptance in Q2, whereas theother experiments unfold their result as a structure function for an average Q2value, F γ2 (x; hQ2i). Figure 1 shows the world summary of the F γ2 measure-ments compared either to hF γ2 (x; Q2)i, assuming a flat acceptance in Q2, or1Invited talk given at the 7th International Workshop on Deep Inelastic Scattering andQCD, April 19 to 23, 1999, Zeuthen, to appear in the proceedings1to F γ2 (x; hQ2i), using the appropriate values for Q2 and hQ2i given by the ex-periments. For the measurements which quote an average virtuality hP 2i ofthe quasi-real photon for their dataset, this value is chosen in the comparison,otherwise P 2 = 0 is used. There is a nice agreement between the data andthe QED expectations for about three orders of magnitude in Q2. The LEPdata are so precise that the eect of the small virtuality of the quasi-real pho-ton can clearly be established, as shown, for example, in Figure 2 for the mostprecise data from OPAL. The data are compared to the QED predictions ofF γ2 (x,hQ2i,hP 2i,m), where either hP 2i or m is varied. Using this data, themass of the muon is found to be m = 0:113 +0:014− 0:017 GeV, assuming the hP 2ivalue predicted by QED. Although this is not a very precise measurement ofthe mass of the muon it can serve as an indication on the precision possible forthe determination of , if it only were for the pointlike contribution to F γ2;had.3 Azimuthal correlationsThe structure functions F γA and FγB are obtained from the measured Fγ2 , anda t to the shape of the distribution of the azimuthal angle , which is theangle between the plane dened by the momentum vectors of the muon pairand the plane dened by the momentum vectors of the incoming and the deeplyinelastically scattered electron. For small values of y, the  distribution can bewritten as:d Nd 1− F γA=F γ2 cos +12F γB=Fγ2 cos 2 : (1)The recent theoretical predictions from Ref. [8] which take into account theimportant mass corrections up to O(m2=W 2), are consistent with the measure-ments of Refs. [4, 5], Figure 3. Both F γA and FγB are found to be signicantlydierent from zero. The shape of F γB cannot be determined very accurately,but it is not compatible with a constant. The best t to a constant F γB/ leadsto 0.032 and 0.042 with 2=dof of 8.9 and 3.1 for the L3 and OPAL resultsrespectively.4 Cross-section for highly virtual photonsThe cross-section for the exchange of two highly virtual photons in the kine-matical region under study can schematically be written as:  TT + TL + LT + LL + (2)12TTcos 2− 4TLcos  : (3)Here the total cross-sections TT, TL, LT and LL and the interference termsTT and TL correspond to specic helicity states of the photons (T=transverse2and L=longitudinal), and  is the angle between the electron scattering planes.There is good agreement between d=dx measured by OPAL, Figure 4, andthe QED predictions using the Vermaseren [9] and the GALUGA [10] MonteCarlo programs, provided all terms of the dierential cross-section are takeninto account. However, as apparent from Figure 4, if either TT (dot-dash) orboth TT and TL (dash) are neglected in the QED prediction as implemented inthe GALUGA Monte Carlo, there is a clear disagreement between the data andthe QED prediction. This measurement clearly shows that both terms, TT andespecially TL, are present in the data in the kinematical region of the OPALanalysis. The contributions to the cross-section are negative and large, mainlyat x > 0:1.As the kinematically accessible range in terms of Q2 and P 2 for the mea-surement of the QED and the QCD structure of the photon is the same, andgiven the size of the interference terms in the leptonic case, special care has tobe taken when the measurements of the QCD structure are interpreted in termsof hadronic structure functions of virtual photons.5 ConclusionsQED has been tested to O(4) using the reaction ee ! eeγ(?)γ? ! ee, andwas found to be in good agreement with all experimental results. Because theprecision of the measurements is limited mainly by the statistical error, signi-cant improvements will be made by using the full expected statistics of 500 pb−1of the LEP2 programme.Acknowledgement:I wish to thank the organisers of this interesting workshop for the fruitful at-mosphere they created throughout the meeting.References[1] R. Nisius, HEP97 Conf., Jerusalem, 1997, hep-ex/9712012; R. Nisius,DIS98 Conf., Brussels, 1998, edited by G. Coremans and R. Roosen, p194{198, World Scientic, 1998.[2] CELLO Collab., H.J. Behrend et al., Phys. Lett. 126B, 384{390 (1983).[3] DELPHI Collab., P. Abreu et al., Z. Phys. C69, 223{234 (1996).[4] L3 Collab., M. Acciarri et al., Phys. Lett. B438, 363{378 (1998).[5] OPAL Collab., G. Abbiendi et al., CERN-EP/99-010, subm. Eur. Phys. J.C.[6] PLUTO Collab., C. Berger et al., Z. Phys. C27, 249{256 (1985).3[7] TPC/2γ Collab., M.P. Cain et al., Phys. Lett. 147B, 232{236 (1984).[8] R. Nisius and M.H. Seymour, Phys. Lett. B452, 409{413 (1999).[9] J.A.M. Vermaseren, Nucl. Phys. B229, 347{371 (1983), and Refs. therein.[10] G.A. Schuler, Comp. Phys. Comm. 108, 279{303 (1998).400.510 0.5 1TPC/2γQ2 = 0.14-1.28 GeV2(a)F 2γ,QED / αF2γ,QED / αOPALQ2 = 2.2 GeV2(b) L3Q2 = 1.4-7.6 GeV2(c)OPALQ2 = 4.2 GeV2(d)xPLUTOQ2 = 5.5 GeV2(e) OPALQ2 = 8.4 GeV2(f)00.511.520 0.5 1CELLOQ2 = 1.4-35 GeV2(g)F 2γ,QED / α DELPHIQ2 = 4-30 GeV2(h) OPALQ2 = 12.4 GeV2(i)OPALQ2 = 21.0 GeV2(j)xPLUTOQ2 = 40. GeV2(k) OPALQ2 = 130. GeV2(l)Figure 1: The world summary on F γ2 measurements. The quoted errors for (h)are statistical only.500.10.20.30.40.50.60.70.80 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1OPALQ2 = 3.0 GeV2(a)xF 2γ,QED / αP2 =    0 GeV2P2 = 0.05 GeV2P2 = 0.10 GeV2mµ = 0.106 GeVOPALQ2 = 3.0 GeV2(b)xF 2γ,QED / αmµ = 0.056 GeVmµ = 0.096, 0.113, 0.127 GeVmµ = 0.156 GeVP2 = 0.05 GeV200.10.20.30.40.50.60.70.80 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Figure 2: The dependence of F γ2 on P2 and on the mass of the muon, m.6-0.25-0.2-0.15-0.1-0.0500.050.10.150.20 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1xFγ A / α OPAL Q2 = 5.4 GeV2Fγ A / αL3 Q2 = 3.25 GeV2 (a)xFγ B / αOPAL Q2 = 5.4 GeV2Fγ B / αL3 Q2 = 3.25 GeV2(b)-0.0500.050.10.150.20 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Figure 3: The measurements of F γA and FγB from L3 and OPAL.701020304050600 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1xdσ / dx [pb](a)< Q2> = 3.6 GeV2< P2> = 2.3 GeV2OPALVermaserenGalugaτTT = 0τTT,τTL = 0xdσ / dx [pb](b)< Q2> = 14.0 GeV2< P2> =  5.0 GeV2OPALVermaserenGalugaτTT = 0τTT,τTL = 00510152025300 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Figure 4: The measurement of the dierential cross section d=dx for highlyvirtual photons from OPAL.8

The QED Structure of the Photon

The spleen is involved in endotoxin-induced interleukin-6 (IL-6) production. To quantitate the relative contribution of the spleen to endotoxin-induced IL-6 production, we studied the effect of endotoxin (1.0 microg/kg of body weight) in control dogs (n = 7) and splenectomized dogs (n = 7). Blood for analysis of tumor necrosis factor (TNF) and IL-6 was sampled from the femoral artery and the portal, hepatic, and splenic (only in controls) veins. Arterial plasma endotoxin and cortisol levels were also measured. Whole-body IL-6 production was calculated by a deconvolution technique. Splenic IL-6 production in control dogs was measured from splenic blood flow and arteriovenous concentration differences. Endotoxin levels were higher in splenectomized dogs (P <0.05) because of a decreased distribution volume (P <0.05) and decreased clearance of endotoxin (P <0.05). Endotoxin-induced plasma IL-6 levels were decreased by approximately 75% in splenectomized dogs (P <0.01), and whole-body IL-6 production rates were severalfold lower (median of 8.7 mg/4 h and range of 3.9 to 11.4 mg/4 h versus a median of 32.3 mg/4 h and a range of 22.7 to 70.2 mg/4 h) (P <0.05). However, in control dogs splenic IL-6 production (0.6 +/- 0.2 mg/4 h) was only approximately 2% of whole-body IL-6 production. Plasma TNF levels increased in both groups (P <0.01) but were not different between the groups. Plasma cortisol levels were slightly higher in splenectomized dogs than in control dogs (P <0.05). In conclusion, splenectomy decreases the distribution volume and clearance rate of endotoxin. Splenectomy results in decreased endotoxin-induced IL-6 production, which is caused not by the absence of splenic IL-6 production, but by a decrease in nonsplenic IL-6 production. Therefore, the spleen is an important mediator in the complete activation of nonsplenic IL-6 production by endotoxi

Moeniralam, H. S.

Bemelman, W. A.

Koopmans, R.

Sauerwein, H. P.

Romijn, J. A.

The decrease in nonsplenic interleukin-6 (IL-6) production after splenectomy indicates the existence of a positive feedback loop of IL-6 production during endotoxemia in dogs

Richard Nisius

MUCC (Crossref)

The QED structure of the photon

UvA-DARE

The QED Structure of the Photon

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