With the completion of the LEP program at CERN, where I had a significant involvement in the study of heavy quark decays with the DELPHI detector, the experiments at the Tevatron and the B factories are now providing new and precise data, ahead of the LHC startup. The analysis of proton-proton collisions at the LHC is expected to answer a number of the fundamental questions on the origin of matter and the new physics beyond the Standard Model. But neither the precise study of the mechanism responsible for mass generation, nor the exploration of signals of New Physics will be completed with the LHC. Since a decade, I am carrying out studies on the physics accessible at a high energy, high luminosity linear collider and R&D work on new detectors needed to fully exploit its potential.

Current Projects

Determination of heavy quark masses through the study of semileptonic decays of the b quark:
The origin of the violation of CP parity, which is a key ingredient for explaining the observed matter anti-matter asymmetry in the Universe, is being studied with the highly accurate measurements obtained at the B factories. But to extract the fundamental parameters from the experimental observables it is necessary to rely on a theory of weak decays of the b quark which involves a number of additional parameters, of which the b and c heavy quark masses are the most important. The level of precision needed to test the origin of the CP violation, requires independent tests of these underlying theory assumptions and accurate measurements of the theory parameters to be performed. A new technique based on the combined analysis of the first moments of distributions of different kinematical observables in semileptonic b decays has been developed and applied to LEP data. The continuation of these studies with more accurate measurements from the Babar, and also the CDF experiments, will allow to test the theory assumptions and to extract precise determinations of the heavy quark masses and of the other parameters necessary to the interpretation of the data on CP violation in the b sector.

Physics studies and Silicon detector R&D for a future high energy, high luminosity linear collider:
There is a wide consensus in the particle physics community that a linear collider, capable of providing electron-positron collisions up to constituent energies comparable to those obtained at the LHC, with high luminosity, is the next step in the exploration of the high energy frontier. A significant activity is ongoing world-wide for reaching the needed specifications for the accelerator components and a concept for the interregional cooperation for its construction and exploitation is presently being outlined. Continuing physics studies are needed to guide the choice of the accelerator parameters and to define the requirements for the detector. We expect to learn from the Tevatron and LHC data if the Higgs mechanism is indeed responsible for the origin of mass and the breaking of the electro-weak symmetry. If a light Higgs boson exists, as suggested from the precision electroweak data, the linear collider will be able to study its properties in great details. New physics signals, such as supersymmetry or extra-dimensions may also be observed and their properties studied precisely. In order to carry out this physics program, the linear collider will require detectors of unprecedented accuracy. In particular the Vertex Tracker, surrounding the beam collision point will need to measure the particle trajectories with a few micron accuracy. The conceptual design of such detector and the choice of the best suited sensor technology will need to be carried out in tight relation with both the physics studies and the design of the accelerator interaction region, capitalising also on the experience gained with the LHC and other large collider detectors.

Complementarity and correlation of cosmology data and future accelerator experiments in Supersymmetry and Extra-dimensions scenarios of Standard Model extensions:
The interplay between the cosmology data and particle physics, presently mostly through the determination of the dark matter density in the Universe and the derivation of constraints on theories introducing a candidate particle for it, represents an exciting research topic across the borders of different fields of physics studies. First, the recent dark matter density measurements guide the choice of well motivated benchmarks in the present studies of physics signatures to be probed at future colliders. They have to represent the variety of experimental signals corresponding to different implementation of New Physics and need to be chosen to comply with present experimental limits on these new phenomena but also reflect other relevant data from low energy experiments and from cosmology. Supersymmetry and models of universal extra dimensions offer specific examples. Once the data provided by the LHC and by a high energy linear collider will become available, not only a candidate dark matter particle can be searched for, but, once a signal will be found, its properties can be thoroughly tested for consistence against the present and forthcoming cosmology data.

Selected Publications

M. Battaglia and L. Gibbons, “Determination of Vub, in Review of Particle Properties,” Phys. Rev. D66, 010001 (2002).

M. Battaglia, et al., “Heavy Quark Parameters and Vcb from Spectral Moments in Semileptonic B Decays,” Phys. Lett. B556, 41 (2003).

M. Battaglia, et al., “Proposed post-LEP Benchmarks for Supersymmetry,” Eur. Phys. J. C22, 535 (2001).

M. Battaglia, “Charting the Higgs boson profile at e+e- linear colliders,” in Proc. of the 10th Int. Conf. on Supersymmetry and Unification of Fundamental Interactions (SUSY02), Hamburg, June 2002.

M. Battaglia and I. Hinchliffe, “The Next Linear Collider,” submitted Physics Today (2003).