The KLOE-2 Experiment at DAΦNE

The KLOE-2 experiment is currently collecting data at DAΦNE the INFN e+e− collider located in the Frascati National Laboratories. The experiment has a wide physics program ranging from: discrete symmetries test, study of light unflavored mesons, searches for light mass for dark matter candidates. In this contribution the upgrade of the detector will be briefly discussed before starting a more detailed presentation on some results concerning: CPT and Lorentz Invariance tests with neutral kaons, dark forces massive boson mediator searches, hadron structure and low energy mesons interaction. 1. KLOE-2 Experiment The KLOE-2 experiment [1] is currently taking data at DAΦNE collider [2][3], the e+e− accelerator of the Frascati National Laboratory running at the φ resonance peak. DAΦNE began operations for KLOE-2 experiment in November 2014 with a new Crab-Waist collision scheme and customized permanent magnet optics in the interaction region [4] to increase the specific luminosity. Several consolidation intervention [5] allowed to deliver 3.0 fb−1 integrated luminosity: 2.4 fb−1acquired that corresponds to 7.4 billion of φ decays. A record peakluminosity of 2.21 × 1032 cm−2s−1 has been achieved. The best daily integrated luminosity has been 13.4 pb−1 and the best weekly integrated luminosity has been 76.3 pb−1. Full time evolution of data delivery is shown in figure 1. The KLOE-2 experiment is an upgraded version of the previous KLOE apparatus with the inclusion of new sub-detectors allowing for larger physics program with increased reconstruction performance. The original KLOE detector consists of a large cylindrical drift chamber (DC) [6] surrounded by a lead-scintillating fiber electromagnetic calorimeter (EMC) [7]. A superconducting coil around the EMC provides a 0.52 T axial field. Two pairs of electron-positron taggers have been installed for γγ physics: a small LYSO crystal calorimeter matrix, the Low Energy Tagger [8] inside KLOE-2 apparatus and a plastic scintillator hodoscope, the High Energy Tagger (HET) [9], along the beam lines outside KLOE-2 detector. To increase the acceptance two new calorimeters have been developed. A pair of LYSO crystal calorimeters (CCALT) [10] have been installed near the interaction region to cover the low-θ range. This calorimeter will be also useful to provide fast signals for luminosity measurement and beam instability feedback to help DAFNE tune-up [11]. 1 on behalf of KLOE-2 Collaboration BEACH 2016 IOP Publishing Journal of Physics: Conference Series 770 (2016) 012010 doi:10.1088/1742-6596/770/1/012010 Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Published under licence by IOP Publishing Ltd 1 Figure 1. Left: time evolution of the DAΦNE data delivery since November 2014. The blue line represent the integrated luminosity delivered, while the red curve is the corresponding amount of integrated luminosity acquired. The black line represent the target luminosity fixed to achieve KLOE-2 goal of 5 fb−1 by the end of KLOE-2 physics run. The black line is horizontal during DAΦNE planned shut-downs (maintenance/laboratory closure). Riht: preliminary results on the residuals between observed and projected impact point with Bhabha scattering events on the outermost plane of the IT. The width of this distribution is the convolution of the IT and DCH resolutions. A pair of tile calorimeters (QCALT) [12], covers the quadrupoles inside KLOE-2 detector and along the beam pipe. These calorimeters are made of tungsten slabs and singly read-out scintillator tiles to improve the angular coverage for particles coming from the active volume of the DC (e.g. KL decay). The most important and challenging upgrade is a multilayer cylindrical GEM [13] tracker for the reconstruction of decay in the vicinity of the primary interaction point (IP). Inner Tracker (IT) is made of four planes covering the tranverse radius interval between 10 and 25 cm from KLOE-2 center. It is expected to double decay vertex resolution at the IP. The current status of alignment of this detector is shown in figure 1. 2. Kaon interferometry Entangled neutral kaon pair can be observed at KLOE-2 because φ decay via strong interaction preserves the φ quantum numbers: JPC = 1−−. For an exhaustive review on this topic refer to [14]. The initial state |φ〉 ∝ |KS, ~ p〉|KL,−~ p〉− |KS,−~ p〉|KL, ~ p〉 evolves preserving the correlation. Observing the two kaons decaying in the same final state (π+π−) as a function of the difference of proper decay times (∆t) the following distribution is expected: If1f2(∆t) ∝ e−ΓΣ |∆t| [ |η1|e ∆Γ 2 ∆t + |ηf2 |2e− ∆Γ 2 ∆t − 2|η1||η2| cos(∆m∆t+ ∆φ12) ] (1) where ΓΣ = ΓS +ΓL, ∆Γ = ΓS−ΓL, ∆m = mKL−mKS and ηj = 〈π π|KL(~ Pj)〉/〈ππ|KS〉 = εK − δK , where εK and δK are the CP and CPT violation parameters in the kaon system, respectively. According to the Standard Model Extension (SME) framework [15] and Greenberg theorem [16], the δK parameter is expressed as: δK ≡ δK(Pμ) ≈ i sinφSW eSW EK mK (∆a0 − ~ PK EK ·∆~a)/∆m, (2) BEACH 2016 IOP Publishing Journal of Physics: Conference Series 770 (2016) 012010 doi:10.1088/1742-6596/770/1/012010