If the mass of dark matter is generated from a cosmological phase transition involving the nucleation of bubbles, the corresponding bubble walls can filter out dark matter particles during the phase transition. Only particles with sufficient momentum to overcome their mass inside the bubbles can pass through the walls. As a result, the dark matter number density after the phase transition has a suppression factor expð−M χ =2γTÞ, where M χ is the dark matter mass, andγ and T are the Lorentz factor and temperature of the incoming fluid in the bubble wall rest frame, respectively. Under certain assumptions, we show that the filtering-out process can naturally provide a large suppression consistent with the observed dark matter density for a wide range of dark matter masses up to the Planck scale. Since the first-order phase transition is the decisive ingredient in our mechanism, a new connection is made between heavy dark matter scenarios and gravitational wave observations.

An analog hadron calorimeter (AHCAL) prototype of 5.3 nuclear interaction lengths thickness has been constructed by members of the CALICE Collaboration. The AHCAL prototype consists of a 38-layer sandwich structure of steel plates and highly-segmented scintillator tiles that are read out by wavelength-shifting fibers coupled to SiPMs. The signal is amplified and shaped with a custom-designed ASIC. A calibration/monitoring system based on LED light was developed to monitor the SiPM gain and to measure the full SiPM response curve in order to correct for non-linearity. Ultimately, the physics goals are the study of hadron shower shapes and testing the concept of particle flow. The technical goal consists of measuring the performance and reliability of 7608 SiPMs. The AHCAL was commissioned in test beams at DESY and CERN. The entire prototype was completed in 2007 and recorded hadron showers, electron showers and muons at different energies and incident angles in test beams at CERN and Fermilab.

A prototype Silicon-Tungsten electromagnetic calorimeter (ECAL) for an International Linear Collider (ILC) detector was installed and tested during summer and autumn 2006 at CERN. The detector had 6480 silicon pads of dimension 1×1 cm 2 . Data were collected with electron beams in the energy range 6 to 45 GeV. The analysis described in this paper focuses on electromagnetic shower reconstruction and characterises the ECAL response to electrons in terms of energy resolution and linearity. The detector is linear to within approximately the 1% level and has a relative energy resolution of (16.6 ± 0.1)/ E(GeV) ⊕ 1.1 ± 0.1 (%). The spatial uniformity and the time stability of the ECAL are also addressed.

Any particle that is charged under SU (3) C and U (1) EM can mediate the gg → γγ process through loops. Near the threshold for the new particle pair production, gauge boson exchanges necessitate the resummation of ladder diagrams. We discuss the leading log order matching of the one-loop result with non-relativistic effective theory resummed result. We show how the diphoton invariant mass spectrum varies depending on decay width, color representation and electric charge of the new particle. The exclusion limits on the product of SU (3) C and U (1) EM charges of the new scalar or fermion particle are obtained from current LHC data. *

Any new particle charged under SU (3)C and carrying electric charge will leave an imprint in the di-photon invariant mass spectrum as it can mediate gg → γγ process through loops. The combination of properties of loop functions, threshold resummation and gluon pdfs can result in a peak-like feature in the di-photon invariant mass around twice the mass of a given particle even if the particle is short-lived and thus it doesn't form a narrow bound state. Using recent ATLAS analysis, we set upper limits on the combined SU (3)C and electric charge of new particles and indicate future prospects. We also discuss the possibility that the excess of events in the di-photon invariant mass spectrum around 750 GeV originates from loops of a particle with mass around 375 GeV.Introduction. As demonstrated by discoveries of the Z boson and the Higgs boson, a resonance is the cleanest signal of a new particle as long as its branching ratios to visible modes are nonzero. However, many popular models including minimal supersymmetric standard model or models with various top-partners predict particles that can be produced in pairs. For the pair production, the searches highly depend on decay modes of a given particle and there are known scenarios in well motivated models which are difficult to see directly even if production cross sections are sizable. In principle, a model can always be constructed in which a new particle cascade decays to complex final states consisting of soft particles and possibly missing energy, or the particle has a large number of possible final states with small branching ratios to individual ones. Signatures that are less model dependent or do not depend on decay modes at all are therefore an integral part of searches for new physics.