English CPH E-Book کتاب الکترونیکی سی. پی.اچ   Welcome to CPH  E-Journal      به نشریه الکترونیکی سی. پی. اچ. خوش آمدید     نسبت پژوهش به جامعه، مانند اندیشه است به انسان- جوادی، کتاب گنجهای نیمه پنهان اظهار نظرها درمورد نظریه سی. پی. اچ تماس با ما سمینارها  اهداف  بنیاد حمایت از نخبگان ایران                    پروژه الکترون پوزیترون               اگر همواره مانند گذشته بينديشيد، هميشه همان چيزهايي را به‌دست مي‌آوريد كه تا بحال كسب كرده‌ايد،  فاينمن

معاونت پژوهشی و فناوری دانشگاه تهران خانه نظریه  سی. پی.اچ

After SPEAR and several other machines around the world had demonstrated the great power of electron-positron colliding beam to produce important new physics results, the next logical step was to increase the energy of such colliders substantially. Both the American and European particle physics communities undertook such a step with the construction of the PETRA storage ring at the DESY laboratory in Hamburg (Germany) and the PEP storage ring at SLAC. PEP, the Positron-Electron Project, was a collaborative effort of SLAC and Lawrence Berkeley Laboratory.

In 1980, PEP began operating and was used for a decade to support the research activities of several hundred physicists and graduate students. The PEP tunnel is about 800 meters in diameter and can produce electron-positron collisions up to center-of-mass energies of about 30 GeV. The PEP physics program did important work measuring the lifetimes of certain elementary particles, studying how the quarks that are initially produced in the collision then fragment or evolve into the various kinds of particles that are actually observed in the detection apparatus, and testing the theory (called Quantum Chromodynamics or QCD) that is presently believed to describe the strong force that binds quarks together. Of particular interest was the observation, made first at PEP, that the B quark had a much longer lifetime than had been anticipated.

As with all storage rings, the particles are kept in their circulating paths by magnets. In PEP, the electron and positron beams each could be stored with energies up to 10 GeV. Experiments at PEP did important work by measuring the lifetimes of B mesons, showing them to be unexpectedly long-lived. Experiments also tested the predictions of the Quantum Chromodynamics or QCD theory that describes the strong force that binds quarks together.

 

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