Naturalness and light Higgsinos: why ILC is the right machine for SUSY discovery

Radiatively-driven natural supersymmetry, a theoretically and experimentally well-motivated framework, centers around the predicted existence of four light, nearly mass-degenerate Higgsinos with mass $\sim 100-200$ GeV (not too far above $m_Z$). The small mass splittings amongst the higgsinos, typically 4-20 GeV, results in very little visible energy arising from decays of the heavier higgsinos. Given that other SUSY particles are considerably heavy, this makes detection challenging at hadron colliders. On the other hand, the clean environment of an electron-positron collider with $\sqrt{s}>2m_{higgsino}$ would enable a decisive search of these required higgsinos, and thus either the discovery or exclusion of natural SUSY. We present a detailed simulation study of precision measurements of higgsino masses and production cross sections at $\sqrt{s}$ = 500 GeV of the proposed International Linear Collider currently under consideration for construction in Japan. The study is based on a Geant4 simulation of the International Large Detector concept. We examine several benchmark points just beyond the HL-LHC reach, with four light higgsinos directly accessible by the ILC, and the mass differences between the lightest SUSY particle and the heavier states ranging from about 4 to 20 GeV. It can be shown that their masses and production cross sections can be precisely measured to approximately 1\% precision or better. These precise measurements allow for extracting the underlying weak scale SUSY parameters, giving predictions for the masses of heavier SUSY states. These provide motivation for future high-energy colliders. Additionally, dark matter properties may be derived. Evolution of the measured gaugino masses to high energies should allow testing the hypothesis of gaugino mass unification.Comment: 6 pages, 4 figures; to appear in the proceedings for EPS-HEP2017, 5-12 July 2017, Venice, Ital

The ILC as a natural SUSY discovery machine and precision microscope: from light higgsinos to tests of unification

The requirement of electroweak naturalness in simple supersymmetric models implies the existence of a cluster of four light higgsinos with mass $\sim 100-300$\,GeV, the lighter the better. While such light compressed spectra may be challenging to observe at LHC, the International Linear $e^+e^-$ Collider (ILC) with $\sqrt{s}>2m_{\rm higgsino}$ would serve as both a SUSY discovery machine and a precision microscope. We study higgsino pair production signatures at the ILC based on full, \texttt{Geant4-}based simulation of the ILD detector concept. We examine several benchmark scenarios that may be challenging for discovery at HL-LHC due to mass differences between the higgsino states between $20$ and $4$\,GeV. Assuming $\sqrt{s}= 500$\,GeV and 1000\,fb$^{-1}$ of integrated luminosity, the individual higgsino masses can be measured to $1-2\%$ precision in case of the larger mass differences, and at the level of $5\%$ for the smallest mass difference case. The higgsino mass splittings are sensitive to the electroweak gaugino masses and allow extraction of gaugino masses to $\sim 3-20\%$ (depending on the model). Extrapolation of gaugino masses via renormalization group running can test the hypothesis of gaugino mass unification. We also examine a case with natural generalized mirage mediation where the unification of gaugino masses at an intermediate scale apparently gives rise to a natural SUSY spectrum somewhat beyond the reach of HL-LHC.Comment: 43 pages, 33 figure

Perhelähtöinen ravintointerventio lastenneuvoloissa - Elintapainterventio Naperoille (ETANA) -esitutkimus

ETANA-tutkimuksessa suunniteltiin ja esitestattiin ravintointerventio, jonka tavoitteena on edistää lapsiperheiden hyviä elintapoja ja tukea ravitsemussuositusten saavuttamista. Intervention toteutusta ja vaikuttavuutta tutkittiin Espoon lastenneuvoloissa toteutetulla Elintapainterventio Naperoille (ETANA) -esitutkimuksella. Tutkimukseen osallistui lapsia, jotka kävivät kahdeksan kuukauden, yhden vuoden ja puolentoista vuoden ikäisten lasten määräaikaisissa terveystarkastuksissa. Tehostettu ravitsemusohjaus kannusti vanhempia lisäämään kasvisten, kalan ja kasviöljyn käyttöä. Tulosten perusteella lastenneuvolan terveysneuvonnan keskeisiä kehittämishaasteita ovat elintapaohjauksen toteuttaminen yksilöllisesti kunkin perheen tarpeiden mukaan, perheen motivointi tarvittavaan muutokseen ja muutoksen saavuttamiseksi tarvittavien keinojen tunnistaminen sekä tavoitteiden saavuttamisen seuranta. Tässä raportissa esiteltävä tutkimus tuottaa näyttöön perustuvaa tietoa terveyden edistämisen työkaluista tutkijoille, asiantuntijoille, päätöksentekijöille sekä terveydenhuoltohenkilöstölle

Dark matter relic density from observations of supersymmetry at the ILC

If supersymmetric particles were discovered at the ILC, would we be able to prove that the dark matter candidate discovered is the only dark matter particle? This was investigated using a scenario with a mostly bino lightest supersymmetric particle and a coannihilating stau. We will demonstrate which measurements and precisions are needed to determine whether the observed dark matter candidate is the sole constituent of the dark matter relic density. The required precisions will be compared to the predicted ILC precisions

Supersymmetry parameter determination at the International Linear Collider

In this thesis, the prospects for determining supersymmetry parameters from observationsof supersymmetric particles at the International Linear Collider (ILC) areinvestigated. Supersymmetry (SUSY) has been proposed in order to solve gaps inthe Standard Model of particle physics, among them the hierarchy problem and theunexplained dark matter content in the universe. There are many free parameters insupersymmetry, whose values give rise to the properties of the supersymmetric particleswhich can be searched for by experiments. While the Large Hadron Collider (LHC)has successfully excluded many possible scenarios, regions of parameter space remainunexplored, especially where the supersymmetric particles decay with little visible energy.For example, models with light higgsinos or scalar tau coannihilation can escapedetection at the LHC. These kinds of scenarios could be discovered or excluded by theproposed ILC, which would collide polarised electron and positron beams at the centreof-mass energy of 500 GeV. The advantages of this machine over the LHC, namely itsthe clean experimental environment and triggerless detector operation, would allow forthe discovery of almost any particle within its kinematic reach.If supersymmetric discoveries were made at the ILC, it would be possible to measurethe properties of the SUSY particles very precisely. These measurements enable determiningsome of the underlying SUSY parameters via tting the parameters to theSUSY observations. In this thesis, a 10-parameter or 13-parameter phenomenologicalMinimal Supersymmetric Standard Model and high-scale 4-6-parameter models(CMSSM, NUHM1 and NUHM2) are tted to sets of possible observations from theILC. Two types of scenarios are considered: light higgsinos motivated by naturalness,and scalar tau coannihilation motivated by the dark matter relic density. It is shownthat the precision measurements of the SUSY and Higgs sectors allow for determiningsome of the SUSY parameters. Additionally, strong predictions for unobserved heavyparticle masses can be made, leading to guidance on future high-energy particle colliders.Furthermore, it is possible under certain circumstances to check whether theobserved particles explain the dark matter relic density. It is shown that the permilleor percent-level measurements from the International Large Detector are crucial formaking these predictions. Additionally, the determined parameters in the weak scalets are evolved to the GUT scale to test the gaugino mass unication hypothesis. Theresults give a strong argument for building an electron-positron collider to close thegaps in the LHC searches or to study any particles that the latter nds

Dark matter relic density from observations of supersymmetry at the ILC

If supersymmetric particles were discovered at the ILC, would we be able to prove that the dark matter candidate discovered is the only dark matter particle? This was investigated using a scenario with a mostly bino lightest supersymmetric particle and a coannihilating stau. In this scenario, the ILC could find the sleptons and lighter gauginos, while the LHC could discover and measure parts of the coloured spectrum. We will demonstrate which measurements and precisions are needed to determine whether the observed dark matter candidate is the sole constituent of the dark matter relic density. The required precisions will be compared to the predicted precisions at the ILC