LHC/ILC Interplay in SUSY Searches

Combined analyses at the Large Hadron Collider and at the International Linear Collider are important to reveal precisely the new physics model as, for instance, supersymmetry. Examples are presented where ILC results as input for LHC analyses could be crucial for the identification of signals as well as of the underlying model. The synergy of both colliders leads also to rather accurate SUSY parameter determination and powerful mass constraints even if the scalar particles have masses in the multi-TeV range.Comment: 5 pages, contribution to the proceedings of EPS0

Strong field effects on physics processes at the Interaction Point of future linear colliders

Future lepton colliders will be precision machines whose physics program includes close study of the Higgs sector and searches for new physics via polarised beams. The luminosity requirements of such machines entail very intense lepton bunches at the interaction point with associated strong electromagnetic fields. These strong fields not only lead to obvious phenomena such as beamstrahlung, but also potentially affect every particle physics process via virtual exchange with the bunch fields. For precision studies, strong field effects have to be understood to the sub-percent level. Strong external field effects can be taken into account exactly via the Furry Picture or, in certain limits, via the Quasi-classical Operator method . Significant theoretical development is in progress and here we outline the current state of play.Comment: 6 pages, ICHEP 2012 Proceeding

Photon collimator system for the ILC Positron Source

High energy e+e- linear colliders are the next large scale project in particle physics. They need intense sources to achieve the required luminosity. In particular, the positron source must provide about 10E+14 positrons per second. The positron source for the International Linear Collider (ILC) is based on a helical undulator passed by the electron beam to create an intense circularly polarized photon beam. With these photons a longitudinally polarized positron beam is generated; the degree of polarization can be enhanced by collimating the photon beam. However, the high photon beam intensity causes huge thermal load in the collimator material. In this paper the thermal load in the photon collimator is discussed and a flexible design solution is presented.Comment: 22 pages, 19 figures, 8 tables, cross-reference to table 4 fixe

Beam Polarization and Spin Correlation Effects in Chargino Production and Decay

We study chargino production e^+ e^- -> chi^+_1 chi^-_1 and the subsequent leptonic decay chi^-_1\to chi^0_1 e^- nu_e including the complete spin correlations between production and decay. We work out the advantages of polarizing the e^+ and e^- beams. We study in detail the polarized cross sections, the angular distribution and the forward--backward asymmetry of the decay electron. They can be used to determine the sneutrino mass m_{\tilde{\nu}_e}.Comment: 14 pages, 17 postscript figures, latex using epsfi

Impact of e^+ and e^- Beam Polarization on Chargino and Neutralino Production at a Linear Collider

We study the production processes e^+ e^- -> chi^+_i chi^-_j, i,j=1,2, and e^+ e^- -> chi^0_m chi^0_n, m,n=1,...,4, working out the advantages of polarizing both beams. For e^+ e^- -> chi^+_1 chi^-_1 with chi^-_1 -> chi^0_1 e^- nu and e^+ e^- -> chi^0_1 chi^0_2 with chi^0_2 -> chi^0_1 e^+ e^- we perform a detailed analysis, including the complete spin correlations between production and decay. We analyze the forward--backward asymmetry of the decay electron for various beam polarizations. We also study polarization asymmetries in e^+ e^- -> chi^0_1 chi^0_2. These asymmetries strongly constrain the gaugino parameter M_1 and the masses m_{\tilde{e}_L}, m_{\tilde{e}_R}, m_{\tilde{nu}} also if m_{\tilde{e}_{L,R}}, m_{\tilde{nu}} > sqrt{s}/2. We give numerical predictions for three scenarios for a linear collider with sqrt{s}=500-1000 GeV.Comment: 26 pages, 26 postscript figures, latex using epsfi

Exploiting Spin Correlations in Neutralino Production and Decay with Polarized e^- and e^+ Beams

We study the production process e^+ e^- -> chi^0_1 chi^0_2 and the subsequent decay chi^0_2 -> chi^0_1 l^+ l^- with polarized e^+ and e^- beams, including the spin correlations between production and decay. We work out the advantages of polarizing both beams. We study in detail the angular distribution and the forward--backward asymmetry of the decay lepton as well as the opening angle distribution between the decay leptons. We investigate the dependence on the masses of tilde{e}_L and tilde{e}_R and on the mixing character of the neutralinos. In particular we study the dependence on the gaugino mass parameter M_1.Comment: 17 pages, 14 postscript figures, latex using epsfi

CP asymmetries in neutralino production in e+e- collisions

We study two CP sensitive triple-product asymmetries for neutralino production e+e- \to\tilde\chi^0_i \tilde\chi^0_j and the subsequent leptonic two-body decay \tilde\chi^0_i \to \tilde l l, \tilde l \to \tilde\chi^0_1 l, for \l= e,\mu,\tau. We calculate the asymmetries, cross sections and branching ratios in the Minimal Supersymmetric Standard Model with complex parameters \mu and M_1. We present numerical results for the asymmetries to be expected at a linear electron-positron collider in the 500 GeV range. The asymmetries can go up to 25 %. We estimate the event rates which are necessary to observe the asymmetries. Polarized electron and positron beams can significantly enhance the asymmetries and cross sections. In addition, we show how the two decay leptons can be distinguished by making use of their energy distributions.Comment: 22 pages, 7 figures; typos corrected, version to appear in Phys. Rev.