What hadron collider is required to discover or falsify natural supersymmetry?

Weak scale supersymmetry (SUSY) remains a compelling extension of the Standard Model because it stabilizes the quantum corrections to the Higgs and W, Z boson masses. In natural SUSY models these corrections are, by definition, never much larger than the corresponding masses. Natural SUSY models all have an upper limit on the gluino mass, too high to lead to observable signals even at the high luminosity LHC. However, in models with gaugino mass unification, the wino is sufficiently light that supersymmetry discovery is possible in other channels over the entire natural SUSY parameter space with no worse than 3% fine-tuning. Here, we examine the SUSY reach in more general models with and without gaugino mass unification (specifically, natural generalized mirage mediation), and show that the high energy LHC (HE-LHC), a pp collider with \sqrt{s}=33 TeV, will be able to detect the SUSY signal over the entire allowed mass range. Thus, HE-LHC would either discover or conclusively falsify natural SUSY with better than 3% fine-tuning using a conservative measure that allows for correlations among the model parameters.Comment: 7 pages; 5 png/pdf figures; revised version coincides with published versio

Gluino reach and mass extraction at the LHC in radiatively-driven natural SUSY

Radiatively-driven natural SUSY (RNS) models enjoy electroweak naturalness at the $10\%$ level while respecting LHC sparticle and Higgs mass constraints. Gluino and top squark masses can range up to several TeV (with other squarks even heavier) but a set of light Higgsinos are required with mass not too far above $m_h\sim 125$ GeV. Within the RNS framework, gluinos dominantly decay via ${\tilde g} \to t{\tilde t}_1^{*},\ \bar{t}{\tilde t}_1 \to t\bar{t}{\widetilde Z}_{1,2}$ or $t\bar{b}{\widetilde W}_1^-+c.c.$, where the decay products of the higgsino-like ${\widetilde W}_1$ and ${\widetilde Z}_2$ are very soft. Gluino pair production is, therefore, signalled by events with up to four hard $b$-jets and large ${\not\!\!{E_T}}$. We devise a set of cuts to isolate a relatively pure gluino sample at the (high luminosity) LHC and show that in the RNS model with very heavy squarks, the gluino signal will be accessible for $m_{{\tilde g}} < 2400 \ (2800)$ GeV for an integrated luminosity of 300 (3000) fb$^{-1}$. We also show that the measurement of the rate of gluino events in the clean sample mentioned above allows for a determination of $m_{{\tilde g}}$ with a statistical precision of $2.5-5\%$ (depending on the integrated luminosity and the gluino mass) over the range of gluino masses where a $5\sigma$ discovery is possible at the LHC.Comment: 25 pages + frontpage. 13 figures consisting of 20 image file

A Rationale for Long-lived Quarks and Leptons at the LHC: Low Energy Flavour Theory

In the framework of gauged flavour symmetries, new fermions in parity symmetric representations of the standard model are generically needed for the compensation of mixed anomalies. The key point is that their masses are also protected by flavour symmetries and some of them are expected to lie way below the flavour symmetry breaking scale(s), which has to occur many orders of magnitude above the electroweak scale to be compatible with the available data from flavour changing neutral currents and CP violation experiments. We argue that, actually, some of these fermions would plausibly get masses within the LHC range. If they are taken to be heavy quarks and leptons, in (bi)-fundamental representations of the standard model symmetries, their mixings with the light ones are strongly constrained to be very small by electroweak precision data. The alternative chosen here is to exactly forbid such mixings by breaking of flavour symmetries into an exact discrete symmetry, the so-called proton-hexality, primarily suggested to avoid proton decay. As a consequence of the large value needed for the flavour breaking scale, those heavy particles are long-lived and rather appropriate for the current and future searches at the LHC for quasi-stable hadrons and leptons. In fact, the LHC experiments have already started to look for them.Comment: 10 pages, 1 figur

Chiral Extensions of the MSSM

We present a class of extensions of the MSSM characterized by a fully chiral field content (no mu-terms) and no baryon or lepton number violating term in the superpotential due to an extra U'(1) gauge symmetry. The minimal model consist of the usual matter sector with family dependent U'(1) charges, six Higgs weak doublets, and three singlets required to give masses to the Higgsinos and cancel anomalies. We discuss its main features such as the tree level mass spectrum and the constraints on flavor changing processes.Comment: 13 pages. V2: Superpotential and U'(1) charges changed. Analysis of the spectrum for the new model added. References update

Constraints on Phases of Supersymmetric Flavour Conserving Couplings

In the unconstrained MSSM, we reanalyze the constraints on the phases of supersymmetric flavour conserving couplings that follow from the electron and neutron electric dipole moments (EDM). We find that the constraints become weak if at least one exchanged superpartner mass is >O(1 TeV) or if we accept large cancellations among different contributions. However, such cancellations have no evident underlying symmetry principle. For light superpartners, models with small phases look like the easiest solution to the experimental EDM constraints. This conclusion becomes stronger the larger is the value of $\tan\beta$. We discuss also the dependence of $\epsilon_K$, $\Delta m_B$ and $b\to s\gamma$ decay on those phases.Comment: 38 pages, 22 figures, uses epsfig.sty, axodraw.sty (not included); error in sign of gluino contribution to EDM of u and d quarks and few figures corrected, important conclusions unchange

Front-end Electronics for Silicon Trackers readout in Deep Sub-Micron CMOS Technology: The case of Silicon strips at the ILC

For the years to come, Silicon strips detectors will be read using the smallest available integrated technologies for room, transparency, and power considerations. CMOS, Bipolar- CMOS and Silicon-Germanium are presently offered in deepsubmicron (250 down to 90nm) at affordable cost through worldwide integrated circuits multiproject centers. As an example, a 180nm CMOS readout prototype chip has been designed and tested, and gave satisfactory results in terms of noise and power. Beam tests are under work, and prospectives in 130nm will be presented

Inflation, moduli (de)stabilization and supersymmetry breaking

We study the cosmological inflation from the viewpoint of the moduli stabilization. We study the scenario that the superpotential has a large value during the inflation era enough to stabilize moduli, but it is small in the true vacuum. This scenario is discussed by using a simple model, one type of hybrid models.Comment: 17 pages, 7 figure

Exotic particles below the TeV from low scale flavour theories

A flavour gauge theory is observable only if the symmetry is broken at relatively low energies. The intrinsic parity-violation of the fermion representations in a flavour theory describing quark, lepton and higgsino masses and mixings generically requires anomaly cancellation by new fermions. Benchmark supersymmetric flavour models are built and studied to argue that: i) the flavour symmetry breaking should be about three orders of magnitude above the higgsino mass, enough also to efficiently suppress FCNC and CP violations coming from higher-dimensional operators; ii) new fermions with exotic decays into lighter particles are typically required at scales of the order of the higgsino mass.Comment: 19 pages, references added, one comment and one footnote added, results unchange

The Reach of the CERN Large Hadron Collider for Gauge-Mediated Supersymmetry Breaking Models

We examine signals for sparticle production at the CERN Large Hadron Collider (LHC) within the framework of gauge mediated supersymmetry breaking models with a low SUSY breaking scale for four different model lines, each of which leads to qualitatively different signatures. We first examine the reach of the LHC via the canonical E_T^miss and multilepton channels that have been advocated within the mSUGRA framework. Next, we examine special features of each of these model lines that could serve to further enhance the SUSY signal over Standard Model backgrounds. We use ISAJET to evaluate the SUSY reach of experiments at the LHC. We find that the SUSY reach, measured in terms of m(gluino), is at least as large, and sometimes larger, than in the mSUGRA framework. In the best case of the co-NLSP scenario, the reach extends to m(gluino) >~ 3 TeV, assuming 10 fb^-1 of integrated luminosity.Comment: 30 page Revtex file plus 12 EPS figure