I. Cohen

The dependence of the emission size on the hadron mass

Abstract The size of the emission volume of pions and kaons, r ππ and r KK , were measured in the hadronic Z 0 decays through the two-pion and two-kaon Bose–Einstein correlations near threshold. Recently the emitter size of the two identical baryons, ΛΛ( Λ Λ ) , was evaluated from the dependence of the fraction of the spin S =1 state on the energy near threshold where it is affected by the Pauli exclusion principle. Here we show that the r dependence on the particle masses, namely the hierarchy r ππ > r KK > r ΛΛ observed in the Z 0 hadronic decays, is well described in terms of the Heisenberg uncertainty principle. A good description can also be obtained via the virial theorem when applied to a general QCD potential. Other available approaches are also discussed.

Møller scattering polarimetry for high energy e+e− linear colliders

Abstract The general features of the M o ller scattering and its use as an electron polarimeter are described and studied in view of the planned future high energy e + e − linear colliders. In particular the study concentrates on the TESLA collider which is planned to operate with longitudinal polarised beams at a centre of mass energy of the order of 0.5 TeV with a luminosity of 3.4×10 34 cm −2 s −1 .

Two-photon physics capabilities of KLOE at DAΦNE

SummaryA feasibility study has been carried out for high-precision measurements of two-photon reactions leading to hadrons at the DAΦNE electron-positron collider. This new facility will operate at a c.m. energy of 1.02 GeV and up to a maximum of 1.5 GeV. It will have a luminosity ofL⋍5·1032 cm−2s−1, 100 times larger than the present available e+e− colliders. DAΦNE offers an excellent opportunity to study γγ reactions at low energy with high statistics, using the KLOE detector equipped with electron tagging facilities as described in this report. Among the various topics that one may address in these studies, we concentrate on the following: 1) Precision measurements of the polarizabilities of charged and neutral pions via the two-photon reactions γγ→ππ. These will allow tests of chiral theories and chiral perturbation techniques, as well as other theoretical approaches. 2) Measurements for the first time of the azimuthal correlations of the γγ→ππ and other two-photon reactions. These provide new tests of the validity of chiral and other theories. 3) Formation of theC=+1 light pseudoscalar mesons, π0, η and η′. This allows the study of the

Precision measurement of the nuclear polarization in laser-cooled, optically pumped 37 K

q\bar q

Precision measurement of the positron asymmetry of laser-cooled, spin-polarized \textsuperscript{37}K

and possibly gluonic inner structure of these mesons. For the π0 its measured radiative width will also improve the currently known lifetime. 4) The possibility to realize a double tagging at DAΦNE will allow reliable measurements of the currently little known total γγ→hadrons cross-section below 1 GeV, to be compared with several models. The physics program described abovecannot be realized without tagging the two-photon reactions to suppress the background from e+e− annihilation channels and other sources.

Precision measurement of the nuclear polarization of laser-cooled, optically pumped 37K

A search for supersymmetric particles (charged scalar leptons, charginos decaying semileptonically, scalar top quarks) and for the associated production of two massive particles decaying into quarks has been performed using a data sample of more than 5 pb−1 at centre-of-mass energies of

Precise Measurement of the Positron Asymmetry in the Decay of Spin-polarized

sqrt{s}=130

^{37}

and 136 GeV collected with the OPAL detector at LEP during November 1995. No evidence for production of any of these particles has been observed in the data. Limits are presented on the production of charged scalar leptons, semileptonically decaying charginos, scalar top quarks and on the associated production of two massive particles leading to four-jet final states.