Fundamental Interactions

PREFACE

CONTENTS

These two lectures are purely pedagogical. My intent is to enable non-experts to get something out of the individual presentations on collider physics that will follow- measurements of the W,Z, top, searches for SUSY, LED's, the Higgs, etc. We often forget that we are talking about instruments and the quantities they actually measure. The surprise is how precise the detectors themselves are; the challenge will be to exploit that precision in the regime where statistics is no longer a problem, and everything is dominated by the performance of the detector (‘systematics’). Precision is necessary not only for measuring numbers such as masses, mixing angles, and cross-sections, but also for searches for new physics, comparing to the Standard Model.

Ultra-relativistic collisions of heavy nuclei at the Relativistic Heavy Ion Collider (RHIC) form an extremely hot system at energy densities greater than 5 GeV/fm³, where normal hadrons cannot exist. Upon rapid cooling of the system to a temperature T ~ 175 MeV and vanishingly small baryo-chemical potential, hadrons coalesce from quarks at the quark-hadron phase boundary predicted by lattice QCD. A large amount of collective (elliptic) flow at the quark level provides evidence for strong pressure gradients in the initial partonic stage of the collision when the system is dense and highly interacting prior to coalescence into hadrons. The suppression of both light (u, d, s) and heavy (c, b) hadrons at large transverse momenta, that form from fragmentation of hard-scattered partons, and the quenching of di-jets provide evidence for extremely large energy loss of partons as they attempt to propagate through the dense, strongly-coupled, colored medium created at RHIC.

In my two lectures, delivered at the 2006 Lake Louise Winter Institute, two topics were addressed: firstly, atomic physics techniques which provide extremely high accuracy as well as sensitivity, and, secondly, tests of symmetries, studies of the forces acting on quantum mechanical systems, and the determination of the fundamental properties of fermions – all performed at low energies. In this contribution to the proceedings of the Winter Institute, mainly the second part is documented whereas only some references are given to the atomic-physics techniques applied.

Neutrinos in the Standard Model of particle physics are massless, neutral fermions that seemingly do little more than conserve 4-momentum, angular momentum, lepton number, and lepton flavour in weak interactions. In the last decade conclusive evidence has demonstrated that the Standard Model's description of neutrinos does not match reality. We now know that neutrinos undergo flavour oscillations, violating lepton flavour conservation and implying that neutrinos have non-zero mass. A rich oscillation phenomenology then becomes possible, including matter-enhanced oscillation and possibly CP violation in the neutrino sector. Extending the Standard Model to include neutrino masses requires the addition of new fields and mass terms, and possibly new methods of mass generation. In this review article I will discuss the evidence that has established the existence of neutrino oscillation, and then highlight unresolved issues in neutrino physics, such as the nature of three-generational mixing (including CP-violating effects), the origins of neutrino mass, the possible existence of light sterile neutrinos, and the difficult question of measuring the absolute mass scale of neutrinos.

This is a mini-series of two lectures where I introduce general concepts of low-energy tests of new physics beyond Standard Model, discuss the effective field theory approach, and review in some detail the current status of searches for permanent electric dipole moments of elementary particles and heavy atoms.

The PHOBOS collaboration has carried out a systematic study of charged particle multiplicities in Cu+Cu and Au+Au collisions at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory. A unique feature of the PHOBOS detector is its ability to measure charged particles over a very wide angular range from 0.5° to 179.5° corresponding to |η| <5.4. The general features of the charged particle multiplicity distributions as a function of pseudo-rapidity, collision energy and centrality, as well as system size, are discussed.

The LHC will provide proton-proton collisions at energies of about 14 TeV and at luminosity up to 10³⁴ cm⁻²s⁻¹. It will be possible to observe new physics but also to have precise measurements of Standard Model phenomena. The perspectives for top quark physics, electro-weak physics, gauge boson couplings and B physics with CMS are briefly discussed here. With the high rate and energy, new processes from the Standard Model, as for example single top, will become visible.

Recent diffractive results from the HI and ZEUS experiments and their comparisons to pQCD models are presented. In particular results on inclusive diffraction as well as exclusive final states such as the diffractive production of D* mesons, dijets and vector mesons are discussed.

In central nucleus-nucleus collisions, deviations from binary scaling at high-p_T reveal themselves as a suppression in the transverse momentum distribution of produced particles as measured by R_cp, the ratio of central to peripheral data scaled by the number of binary collisions. The system size dependence of R_cp may help disentangle the interplay of initial (e.g. gluon saturation) and final (e.g. parton energy loss) state effects which are thought to modify the scaling behavior of the high-p_T suppression. Here we present results on R_cp of charged hadrons from the BRAHMS experiment comparing results from AuAu, CuCu and dAu collisions.

In these proceedings, the preliminary non-photonic electron spectra from p + p, d + Au and Au + Au collisions at at mid-rapidity are presented. The momentum range of reconstructed non-photonic electrons is 1.5 < p_T < 10 GeV/c. The dominant contribution to the non-photonic electron spectrum is the semi-leptonic decay of D and B mesons. The electron nuclear modification factor (R_AA) shows a large suppression in central Au+Au collisions, indicating an unexpectedly large energy loss for heavy quarks in the hot and dense matter created at RHIC. Theoretical models tend to overpredict the data if the contributions from both charm and beauty decays are taken into account.

After firmly establishing direct CP Violation in two pions decays of neutral kaons, the NA48 experiment, during the 2003 run at CERN-SPS, has collected more than 1.6 billion of charged kaon decays into three charged pions, using a unique double beam technique which allows a high level of control on systematic effects. The measurement of the direct CP violation Dalitz plot linear slope asymmetry parameter A_g is reported. This result corresponds to more than an order of magnitude improvement in precision with respect to previous experiments and is limited by the statistics of the data sample.

A brief overview of AMANDA and IceCube is presented, with an introduction into the basic physics and detection principles and a small selection of the results.

A review of recent searches for direct CP violation in charmless B decays is given. Reported analyses were performed on a data sample containing about pairs collected with the Belle detector operating at the KEKB e⁺e⁻ collider.

The Standard Model, despite its open questions, has proved its consistency and predictive power to very high accuracy within the currently available energy reach. LHC, with its high CM energy and luminosity, will give us insight into new processes, possibly showing evidence of “new physics”. Excellent understanding of the SM processes will also be a key to discriminate against any new phenomena. Prospects of selected SM measurements with the ATLAS detector using early LHC luminosity are presented.

Among the measured leptonic B decays in the world so far, there is no signal found except the decay . We review the data analysis methods in each experiment and compare the experimental upper limits of the branching fraction with the Standard Model predictions.

The CMS potential for the Higgs boson discovery is discussed in the framework of the Standard Model (SM) and its Minimal Supersymmetric extension (MSSM).

During the past years, many new physics searches have taken place at HERA. These include model-based searches, like SUSY or leptoquarks studies, but also many final-states studies. In the first case, limits could be put on many parameters of these models. In the latter, HI saw an excess in the isolated leptons channel, which was not confirmed by ZEUS. This excess also appears in the multi-leptons search of HI.

Presented are recent electroweak results from the DØ experiment.

At the LHC, the program of research in particle physics beyond the Standard Model is extremely rich. With the ATLAS detector, besides SUSY mainstream studies, many exotic theoretical models will be investigated. They range from compositeness of fundamental fermions to extra dimension scenarii through GUT models and include many variants. I shall review some selected typical studies by the ATLAS collaboration on exotic physics, highlighting the discovery prospects and the recent analyses using the latest full detector simulations.

In order to get ready for physics at the LHC, the CMS experiment has to be set up for data taking. The data have to be well understood before new physics can be investigated. On the other hand, there are standard processes, well known from previous experiments and from simulation, which will help to understand the data of the detector in the early days of the LHC.

We report on the new measurements of W and Z cross sections times Ieptonic branching ratios in collisions at the Tevatron at . The measurements are based on the decays W → eν, Z → μ⁺μ⁻ and Z → ττ.

The Belle experiment at the KEKB asymmetric e⁺e⁻ collider has proven to be an excellent experimental environment for a wide variety of measurements. These include observations of several previously undiscovered particles and measurements of their properties. While some of these states are predicted in different models, other pose questions regarding their nature and represent a challenge for the description in terms of QCD. A short overview of experimental knowledge on X(3872), Z(3930), Y(3940) and X(3940) is presented.

We show that the enhancement of the ν-N cross section due to new physics is suppressed in models that include a minimal length scale, resulting in a strongly reduced potential observation rate of micro black holes at neutrino telescopes.

We report the results of three searches for lepton-flavor and lepton-number violations in the decay of the tau lepton. The analyses have been performed with around 2 × 10⁸ e⁺e− → τ⁺τ⁻ events collected by the BABAR detector at the PEP-II storage ring at a center-of-mass energy near 10.58 GeV. A search for the nonconservation of lepton flavor number in the decay τ^± → μ^± γ yielded no evidence for a signal and we set an upper limit on the branching ratio of B(τ^± → μ^±γ) < 6.8 × 10⁻⁸ at 90% confidence level. In the search for the non-conservation of lepton flavor in the decay τ^± → e^± γ we find no evidence for a signal and set an upper limit on the branching ratio of B(τ^± → e^±γ) < 1.1 × 10⁻⁷ at 90% confidence level. A search for lepton-flavor and lepton-number violation in the decay of the tau lepton into one charged lepton and two charged hadrons was performed in 14 different decay modes. The observed data are compatible with background expectations, and upper limits are set in the range B(τ^± → ℓhh) < (0.7 − 4.8) × 10⁻⁷ at 90% confidence level. The results of these three analyses have been published in ¹²³.

Measurements of time-dependent CP asymmetries in B⁰ → J/ψK⁰, φK⁰, K⁺K⁻ K_S, _η′ K_S, f₀ (980) K_S and ωK_S decays based on 386 × 10⁶ pairs collected by the Belle detector are presented. With this data sample, the J/ψK⁰ mode provides a precision measurement of sin2 φ₁. The other modes, which proceed via b → s penguin (loop) diagrams are sensitive to new physics phases which may appear within the loop. Differing sin2 φ₁ measurements between J/ψK⁰ and the b → s penguin modes could be a signature of such phases.

For the first time, beam-spin and beam-charge azimuthal asymmetries have been measured in electroproduction of hard photons on nuclei ranging from Deuterium to Krypton. The asymmetry results from the interference between the Bethe-Heitler and deeply virtual Compton scattering processes. The data have been obtained in the period from 1998 to 2000 by the HERMES experiment at HERA/DESY by scattering the 27.6 GeV longitudinally polarized lepton beam off an internal gas target. The final running period of HERMES until 2007 is dedicated to hard exclusive reactions. A recoil detector surrounding the gas target was installed and is currently being commissioned.

We present the first measurement of the forward-backward asymemtry and the ratios of Wilson coefficients A₉/A₇ and A₁₀/A₇ in B → K*ℓ⁺ℓ⁻, where ℓ represents an electron or a muon. The results are obtained from a data sample containing 386 million pairs that was collected on the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric energy e⁺e⁻ collider.

MINOS (Main Injector Neutrino Oscillation Search) is an accelerator-based long-baseline experiment designed to measure the properties of neutrino oscillations. MINOS will be able to provide a greater understanding of neutrino oscillations by making precision measurements of the neutrino mixing parameters in the atmospheric Δm² range. A neutrino beam generated by the NuMI facility at Fermilab is directed towards the Soudan Mine, located 735 km away in northern Minnesota. The MINOS Near Detector at Fermilab measures the neutrino beam energy spectrum, which is then extrapolated to predict the non-oscillated neutrino energy spectrum at the Far Detector located in the Soudan Mine. The ratio of the observed energy spectrum to the predicted energy spectrum at the Far Detector provides the measurement of and sin²2θ_atm. MINOS has been taking data from the neutrinos delivered through the NuMI beamline since early 2005. In this talk, I present the physics goals, the current status of the experiment and the analysis of the first year of data.

In models with large extra dimensions (LXDs) the Planck scale can be lowered to values that are within the reach of the next generation of particle colliders. Those models predict the production of TeV mass black holes and therefore a new era in short distance physics. However, the details of the black hole evaporation process especially in the final phase are unknown. We study the implications of the assumption that a quasi stable remnant is formed. Therefore the black hole particle spectrum and direct detection are taken into account.

The idea of incorporating the particle content of a field theory as a mild noncom-mutativity in its geometry is revisited. An adjustment to the Lorentzian signature of the universe is discussed.

A search for oscillations was performed with a sample of semileptonic decays corresponding to approximately 610 pb⁻¹ of integrated luminosity accumulated with the DØ Detector in Run II at Fermilab (Tevatron). The flavor of the final state of the meson was determined using the muon charge from the partially reconstructed decay , An opposite-side tagging method was used for the initial-state flavor determination. A 95% confidence level limit on the oscillation frequency Δm_s > 7.3 ps⁻¹ and sensitivity 9.5 ps⁻¹ were obtained.

LHCb is a dedicated B-physics experiment at the LHC. It is currently under construction, to be ready for first collisions in 2007. We give an overview of the expected physics performance: sensitivity in typical channels for study of mixing, CP violation and rare B decays.

The helicity density of the strange quark sea in the proton has been extracted from measurements of polarized semi-inclusive production of charged kaons in deep inelastic scattering of positrons from a polarized deuteron target. The isoscalar nature of the deuteron (assuming isospin symmetry) and lack of isospin for strange quarks allows the deuteron target to be used independently without relying on fragmentation models or other experimental data. In the region of measurement x > 0.02 the helicity density is zero within the experimental error and agrees with a previous five flavor extraction performed by HERMES. The first moment of the axial charge in the measured region is substantially less than that inferred from LO (NLO) QCD fits that cover the entire x-range.

At HERA, electroweak physics can be investigated in deep inelastic scattering. The HI experiment determined QCD and electroweak paramters simultaneously for the first time in a global fit to the cross sections measured at HERA I. At HERA II, the longitudinal polarisation of the lepton beam gives access to the chiral properties of neutral and charged current interactions at high momentum transfers. Due to the higher luminosity, the number of candidate events for single W production has increased, but still more statistics is needed to draw final conclusions.

We present recent results on purely leptonic and electroweak penguin decays of the B meson based on data samples of up to 232 million pairs collected by the BABAR experiment at the PEP-II B-Factory at SLAC. We present measurements of the branching fraction, the direct CP violating asymmetry, and photon energy spectrum of B → X_sγ decays using both a fully inclusive lepton-tagged technique as well as a sum of exclusive final states. Also included are results on the decay rates and asymmetries for the decays B → K^(*) ℓ⁺ℓ⁻. Finally, we present a search for the fully-leptonic decay B⁺ → τ⁺ν_τ.

The COBRA experiment aims to use a large quantity of CdZnTe semiconductor detectors to search for neutrinoless double beta decay. The current status of the experiment is discussed, and new limits on several double beta modes are presented. Future plans for a large scale experiment are also described.

Proton structure as measured up until now by ep collisions at HERA is reviewed, and some issues to be tackled further are addressed.

LHCb is a next-generation forward spectrometer for CP violation measurements, using the Large Hadron Collider at CERN. In order to achieve its goals a high overall track reconstruction performance is needed. The LHCb tracking system comprises three main sub-systems: the vertex locator, the trigger tracker and the downstream tracking stations.

The BaBar experiment at the PEP-II B-factory offers excellent opportunities in quarkonium spectroscopy. Investigation of the properties of new states like the X(3872) and y(4260) are performed, aiming to shed light on their nature. Recent BaBar results in this field are presented.

We present the results for the measurement of γ in the BABAR experiment which exploit the interference between the V_ub and V_cb mediated amplitudes in the B → DK and B → Dπ systems. Experimental details along with future prospects are discussed.

Searches for New Physics beyond the Standard Model have been performed with the DØ detector at the Tevatron collider (Fermi National Accelerator Laboratory) at . Using a Run II data set of ~ 350 pb⁻¹, various analyses have covered a multitude of signatures, reaching sensitivity in parameter regions well beyond existing limits. No significant deviation from the Standard Model has been observed while searching for supersymmetry, leptoquarks and neutral long-lived particles.

With the large amount of data recorded by the BABAR experiment at the ϒ (4S) energy, and in particular, using charm pairs coming from the continuum, a diversity of charm physics analyses can be addressed. In this talk, recent results on the Dalitz plot analysis of the D⁰ → K_sK⁺K⁻ decay, and on charm baryon properties are presented.

Two-gluon radiative corrections to the decay rate in the kinematical limit have been calculated as an expansion around . In combination with known expansion around , these results describe the corrections in the whole range of final quark mass with accuracy much better than 1%.

The top quark is the most massive fundamental particle observed so far, and the study of its properties is interesting for several reasons ranging from its possible special role in electroweak symmetry breaking to its sensitivity to physics beyond the Standard Model (SM). This article will focus on the latest top physics results from CDF based on 320-750 pb⁻¹ of collision data at . The cross section and the top mass have been measured in different decay channels and using different methods. We have also searched for massive resonances.

We determine the di-electron widths of the ϒ (1S), ϒ (2S), and ϒ (3S) resonances with better than 2% precision by integrating the cross-section of e⁺e⁻ → ϒ over the e⁺e⁻ center-of-mass energy. Using e⁺e⁻ scans of the ϒ resonances at the Cornell Electron Storage Ring and measuring ϒ production with the CLEO detector, we find di-electron widths of 1.252 ± 0.004 (σ_stat) ± 0.019 (σ_syst) keV, 0.581 ± 0.004 ± 0.009 keV, and 0.413 ± 0.004 ± 0.006 keV for the ϒ (1S), ϒ (2S), and ϒ (3S), respectively.

The CMS experiment at the LHC is building an electromagnetic calorimeter with high performance. Preserving high reconstruction efficiency and best four momentum measurements for electrons is a necessity for optimal discovery prospects in the ZZ^(*) and WW^(*) Higgs boson decay channels. This is challenging in view of the material budget in front of ECAL and of the presence of a strong magnetic field. A new reconstruction strategy for electrons in CMS is described. The usage of electrons from single Z and W production for the ECAL calibration strategy is also discussed.

The AMS-01 magnetic spectrometer that flew on the Space Shuttle for ten days and the AMS-02 experiment that will be on the International Space Station for three years offer unique looks at cosmic rays. While the majority of cosmic rays come from astrophysical sources, a small component may be from the annihilation of weakly interacting dark matter particles. We outline our current progress in a search for such a component in the negatively charged particles seen in the AMS-01 detector. This includes simulation of the production of cosmic rays from dark matter annihilation, their propagation through the galaxy, and the signal they would leave in the AMS-01 detector.

ATLAS is a general purpose p-p collider detector being constructed for the CERN Large Hadron Collider (LHC). It is located in one of the two high luminosity bunch crossing points (peak luminosity of 10³⁴cm⁻²s⁻¹) of the LHC. It consists of 3 main sections. Located close to the beam axis, the tracking system employs pixel detectors, silicon microstrip modules and transition radiation straws, all within a 2 Tesla superconducting solenoid. The tracker is surrounded by the electromagnetic and hadronic calorimeters. In the outer part of the detector, 8 superconducting coils define an open toroidal magnetic field for muon detection. The construction status of the ATLAS detector towards being ready for the first collisions in 2007 will be presented, with particular emphasis on the construction and projected performance of the tracking system.

We present preliminary measurements of the cross section and the double longitudinal spin asymmetry in inclusive jet production in polarized p+p collisions at . The measured cross section agrees well with NLO pQCD calculations over seven orders of magnitude. The observed spin asymmetries are consistent with theoretical evaluations based on deeply inelastic scattering data and tend to disfavor a large positive gluon polarization.

We report on recent results from the Collider Detector at Fermilab (CDF) experiment, which is accumulating data from proton-antiproton collisions with at Run II of the Fermilab Tevatron. The new phenomena being explored include Higgs, Supersymmetry, and large extra dimensions. We also present the latest results of broad searches for heavy objects, including Z′ bosons and heavy quarks.

The review of the main analyses on the W Physics at LEP2 is presented. The measurement of the W decay branching ratios is a test of the lepton universality and the CKM matrix unitarity. The study of the WW cross section to prove the non-abelian structure of the SU(2)_L × U(1)_Y gauge simmetry. The direct reconstruction of WW invariant mass allows the precise measurement of the W mass.

The PICASSO experiment, located in the Creighton Mine in Sudbury, Ontario, Canada, has demonstrated the viability of the superheated droplet technique in direct dark matter detection. Experimental sensitivity is to spin dependent elastic collisions with ¹⁹F as the active mass. Limits of σ_p = 1.31pb and σ_n = 21.5pb on the WIMP-proton and WIMP-neutron cross-sections respectively, at a 90% C.L. for a WIMP mass of 29 GeV/c² were determined in 2004¹ using a small scale setup with 20g of active mass. Details of the PICASSO experiment, along with the improvements incorporated into the upcoming PICASSO 32 phase will be outlined in these proceedings.

The LHCb particle identification system is presented. The system consists of two Ring-Imaging Cherenkov detectors which provide pion/kaon separation over the momentum range 1 to 100 GeV/c, the Calorimeter system, with which it is possible to identify neutral particles, and the Muon Detector.

We report CDF results on the meson ¹ in Run II. The meson has been observed in semileptonic decays, , where ℓ = e, μ at a significance greater than 5σ in both channels. The observations have resulted in measurements of the relative production times branching ratio with respect to B⁻ → J/ψ K⁻ decays and a precise determination of the lifetime of the . Also, an observation of decays at a significance exceeding 6σ results in a precise determination of the mass of the .

Azimuthal single spin asymmetries (SSA) in semi inclusive deep inelastic lepton scattering (SIDIS) provide a tool to access transversity, the distribution of transversely polarized quarks in a transversely polarized nucleon. Using a transversely polarized hydrogen target SSA are measured for positively and negatively charged pions. For both particle types the extracted Collins moments are significantly different from zero in the kinematic region covered by the HERMES detector.

LIST OF PARTICIPANTS