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Register a new userCrab Waist Collision Studies for e+e- Factories
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Numerical simulations have shown that the recently proposed crab waist scheme of beam-beam collisions can substantially boost the luminosity of existing and future electron-positron colliders. In this paper we describe the crab waist concept and discuss potential advantages that such a scheme can provide. We also present the results of beam-beam simulations for the two currently proposed projects based on the crab waist scheme: the DAFNE upgrade and the Super B-factory project.
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We present results from luminosity, energy and polarization studies at a future Linear Collider. We compare e+e- and e-e- modes of operation and consider both NLC and TESLA beam parameter specifications at a center-of-mass energy of 500 GeV. Realistic colliding beam distributions are used, which include dynamic effects of the beam transport from the Damping Rings to the Interaction Point. Beam-beam deflections scans and their impact for beam-based feedbacks are considered. A transverse kink instability is studied, including its impact on determining the luminosity-weighted center-of-mass energy. Polarimetry in the extraction line from the IP is presented, including results on beam distributions at the Compton IP and at the Compton detector.
The Phi-factory DAFNE was upgraded in the second half of 2007 in order to implement a recently proposed scheme of crab waist collisions aimed at substantial luminosity increase. Commissioning of the modified collider started in November 2007. In this paper we briefly describe the crab waist collision concept and discuss in detail the DAFNE hardware upgrade and obtained experimental results.
High Luminosity upgrades of the KEK-B collider are being discussed. We consider the role of the purely leptonic decays B^pm -> l^pm nu and B^0 -> l+l- in motivating such an upgrade. These decays are very sensitive to R parity violating extensions of the MSSM, and we show that future runs of the KEK-B factory can be competitive with high energy colliders for probing such models.
The e-e- running mode is one of the interesting physics options at the International Linear Collider (ILC). The luminosity for e-e- collisions is reduced by the beam-beam effects. The resulting beamstrahlung energy loss and beam-beam deflection angles as function of the vertical transverse offset are different compared to the e+e- collisions. In this paper, the dependence of these observables with the offset for different beam sizes has been analyzed to optimize performances for the e-e- mode, taking into account the requirements of the beam-beam deflection based intra-train feedback system. A first study of the implications for the final focus and extraction line optics is also presented for the cases of the 20 mrad and 2 mrad ILC base line crossing angle geometries.
By including the interference effect between the QCD and the QED diagrams, we carry out a complete analysis on the exclusive productions of $e^+e^- to J/psi+chi_{cJ}$ ($J=0,1,2$) at the $B$ factories with $sqrt{s}=10.6$ GeV at the next-to-leading-order (NLO) level in $alpha_s$, within the nonrelativistic QCD framework. It is found that the $mathcal O (alpha^3alpha_s)$-order terms that represent the tree-level interference are comparable with the usual NLO QCD corrections, especially for the $chi_{c1}$ and $chi_{c2}$ cases. To explore the effect of the higher-order terms, namely $mathcal O (alpha^3alpha_s^2)$, we perform the QCD corrections to these $mathcal O (alpha^3alpha_s)$-order terms for the first time, which are found to be able to significantly influence the $mathcal O (alpha^3alpha_s)$-order results. In particular, in the case of $chi_{c1}$ and $chi_{c2}$, the newly calculated $mathcal O (alpha^3alpha_s^2)$-order terms can to a large extent counteract the $mathcal O (alpha^3alpha_s)$ contributions, evidently indicating the indispensability of the corrections. In addition, we find that, as the collision energy rises, the percentage of the interference effect in the total cross section will increase rapidly, especially for the $chi_{c1}$ case.
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