Luminosity and background measurements at the e + e  DAFNE collider upgraded with the crab waist scheme M. Boscolo a , F. Bossi a , B. Buonomo a , G. Mazzitelli a , F. Murtas a , P. Raimondi a , G. Sensolini a , M. Schioppa b , F. Iacoangeli c , P. Valente c , N. Arnaud d,Ã , D. Breton d , L. Burmistrov d , A. Stocchi d , A. Variola d , B. Viaud d , P. Branchini e a INFN/LNF, Via E. Fermi 40-00044, Frascati, RM, Italy b Gruppo Collegato INFN, Via P. Bucci - 87036, Rende, CS, Italy c INFN Roma, P.le Aldo Moro 5, Roma, Italy d Laboratoire de l’Acce´le´rateur Line´aire, Universite´ Paris-Sud, CNRS/IN2P3, 91898 Orsay, France e INFN Roma 3, Via della Vasca Navale, 84 - 00146 Roma, Italy article info Article history: Received 10 July 2009 Received in revised form 29 March 2010 Accepted 13 April 2010 Available online 24 April 2010 Keywords: Luminosity DAFNE Crab waist Calorimeter Bhabha scattering abstract The crab waist collision scheme has been successfully tested at the e + e  Frascati collider during the 2008–2009 runs: the gain in luminosity is consistent with the predictions while the background remains sustainable. Among the various inputs used by the DAFNE accelerator team to steer this new machine and improve its performances, key online information, absolute luminosity and background level measurements, has been provided by the LUMI detectors: a Bhabha calorimeter and two gamma bremsstrahlung proportional counters. This paper focuses on the results achieved with this experimental setup, described in details in another article. & 2010 Elsevier B.V. All rights reserved. 1. Introduction Proposals of future flavor factories [1–3] emphasize the need of very high luminosity. For instance, the new generation of B-factories [1,2] requires improvements up to two orders of magnitude above the performances of the PEP-II [4] and KEK-B [5] e + e  colliders. Among the ideas currently being developed to achieve this ambitious physics-driven goal, the crab waist compensation scheme associated with large Piwinski angle and low vertical beta function [6] is very promising. Luminosities as high as 10 36 cm 2 s 1 could be reached with beam currents similar to those operated routinely in today’s accelerators, which would also help keeping the background under control. In addition to being based on existing technologies, this scheme would significantly limit the power (and hence the cost) needed to run such a new machine. The DAFNE accelerator, located in the National Laboratory of Frascati (INFN), is optimized for the production of f mesons ð ffiffi s p ¼ 1020 MeVÞ at a high rate. Since 2000 it has been delivering e + e  collisions to three experiments KLOE [7], FINUDA [8] and DEAR [9], steadily improving performances in terms of luminos- ity, beam lifetimes and background. The best peak luminosity was  1:5  10 32 cm 2 s 1 with typical daily integrated luminosities of  8 pb 1 during the KLOE run. In 2007, the DAFNE interaction point 1 (IP) has been modified to test the crab waist sextupole compensation scheme [6]. According to calculations, this upgrade should increase the luminosity by a factor between 3 and 5. To test this prediction and to measure the associated background, various detectors have been built around the IP by the LUMI collaboration: a Bhabha calorimeter, a GEM [10] tracker and two gamma monitors. By providing accurate information to the DAFNE operators in real time, they aim at allowing them to steer the collider, to monitor its performances and to get direct feedback when performing optimization studies. There is some redundancy between their measurements which helps fighting transient backgrounds which could impact strongly a particular detector. It should be noted that the SIDDHARTA experiment [11], installed at the same location, can in principle provide a luminosity measurement by counting kaon pairs produced by the well-known decay f-K þ K  . However, this method suffers from a few practical limitations. The main ones are: a low rate for the K + K  production; a difficult event rate to luminosity conversion due to the dependence of the F resonance lineshape on the exact Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/nima Nuclear Instruments and Methods in Physics Research A 0168-9002/$ - see front matter & 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2010.04.044 Ã Corresponding author. Tel.: + 33 1 64 46 89 17; fax: + 33 1 64 46 85 46. E-mail address: narnaud@lal.in2p3.fr (N. Arnaud). Nuclear Instruments and Methods in Physics Research A 621 (2010) 121–129