We present a 6 orbifold compactification of the E8 × E8 heterotic string which leads to the (supersymmetric) Standard Model gauge group and matter content. The quarks and leptons appear as three 16-plets of SO(10), whereas the Higgs fields do not form complete SO(10) multiplets. The model has large vacuum degeneracy. For generic vacua, no exotic states appear at low energies and the model is consistent with gauge coupling unification. The top quark Yukawa coupling arises from gauge interactions and is of the order of the gauge couplings, whereas the other Yukawa couplings are suppressed.

We show that in the case of small R-parity and lepton number breaking couplings, primordial nucleosynthesis, thermal leptogenesis and gravitino dark matter are naturally consistent for gravitino masses m 3/2 > ∼ 5 GeV. We present a model where R-parity breaking is tied to B-L breaking, which predicts the needed small couplings. The metastable next-to-lightest superparticle has a decay length that is typically larger than a few centimeters, with characteristic signatures at the LHC. The photon flux produced by relic gravitino decays may be part of the apparent excess in the extragalactic diffuse gamma-ray flux obtained from the EGRET data for a gravitino mass m 3/2 ∼ 10 GeV. In this case, a clear signal can be expected from GLAST in the near future.

We investigate the cosmological moduli problem by studying a modulus decay in detail and find that the branching ratio of the gravitino production is generically of O(0.01 − 1), which causes another cosmological disaster. Consequently, the cosmological moduli problem cannot be solved simply by making the modulus mass heavier than 100 TeV. We also illustrate our results by explicitly calculating the branching ratio into the gravitinos in the mixed modulus-anomaly/KKLT-and racetrack-type models.The cosmological moduli problem [1] is one of the most challenging puzzles in particle physics and cosmology. In this letter, we show that the problem is even more difficult than usually thought.In supergravity/superstring theories, generically there exist moduli fields which have flat potentials and obtain masses from supersymmetry (SUSY) breaking and nonperturbative effects. During an inflationary period, a modulus field X is likely to develop a large expectation value. After the end of the inflation, it starts a coherent oscillation and soon dominates the energy density of the universe. Due to the interaction suppressed by the Planck scale M P = 2.4 × 10 18 GeV, the decay rate of the modulus X is extremely small:which leads to an onset of a radiation-dominated universe with a very low temperature:Here, c is an order one coefficient and g * is the effective number of massless degrees of freedom. This is cosmologically unacceptable because a successful big-bang nucleosynthesis (BBN) requires that the (last) radiationdominated universe starts with temperature higher thanAs is clear from Eq. (2), a simple solution would be to assume that the modulus X is ultra heavy a :Actually, there have been proposed scenarios with such a large modulus mass (cf. [5,6,7,8,9]). However, there exists yet another serious cosmological obstacle even for heavy moduli scenarios. The new problem is caused by the gravitino which is produced by the modulus decay. Indeed, as we will show, the branching a See Refs. [3,4] for other solutions. ratio of the modulus decay into the gravitino is generically quite largewhich causes serious problems after the modulus decay. We call this problem the moduli-induced gravitino problem.The gravitino production via modulus decay and its cosmological implications have been previously discussed in Refs. [10,11], taking Br(X → gravitino) ≪ 1. The main purpose of this letter is to show that Eq. (4) holds in a generic setup, and to emphasize how disastrous its consequences are. We also exemplify explicit results in the mixed modulus-anomaly/KKLT mediation [6,7] and in the racetrack [8] setups.Let us first estimate the branching ratio of a modulus decay into gravitino(s). We consider a heavy modulus scenario, m X > ∼ 100 TeV [cf. Eq. (3)]. On the other hand, the gravitino is likely to be (much) lighter than 100 TeV, because too large gravitino mass requires a finetuning in the Higgs sector due to the anomaly-mediated effects. Thus, we assume m X ≫ m 3/2 hereafter. After choosing the unitary gauge in the Einstein frame, w...

Physics at the Large Hadron Collider (LHC) and the International e + e − Linear Collider (ILC) will be complementary in many respects, as has been demonstrated at previous generations of hadron and lepton colliders. This report addresses the possible interplay between the LHC and ILC in testing the Standard Model and in discovering and determining the origin of new physics. Mutual benefits for the physics programme at both machines can occur both at the level of a combined interpretation of Hadron Collider and Linear Collider data and at the level of combined analyses of the data, where results obtained at one machine can directly influence the way analyses are carried out at the other machine. Topics under study comprise the physics of weak and strong electroweak symmetry breaking, supersymmetric models, new gauge theories, models with extra dimensions, and electroweak and QCD precision physics. The status of the work that has been carried out within the LHC / LC Study Group so far is summarised in this report. Possible topics for future studies are outlined.4

If the gravitino mass is in the region from a few GeV to a few 10's GeV, the scalar lepton X such as stau is most likely the next lightest supersymmetry particle. The negatively charged and longlived X − may form a Coulomb bound state (AX − ) with a nucleus A and may affect the big-bang nucleosynthesis through catalyzed fusion process. We calculate a production cross section of 6 Li from the catalyzed fusion ( 4 HeX − ) + d → 6 Li + X − by solving the Schrödinger equation exactly for three-body system of 4 He, d and X. We utilize the state-of-the-art coupled-channel method, which is known to be very accurate to describe other three-body systems in nuclear and atomic reactions. The importance of the use of appropriate nuclear potential and the exact treatment of the quantum tunneling in the fusion process are emphasized. We find that the astrophysical S-factor at the Gamow peak corresponding to T = 10 keV is 0.038 MeV barn. This leads to the 6 Li abundance from the catalyzed process as 6 Li| CBBN ≃ 4.3 × 10 −11 (D/2.8 × 10 −5 )([n X − /s]/10 −16 ) in the limit of long lifetime of X. Particle physics implication of this result is also discussed.