arXiv subjects

Teruki Kamon

Publications and source records attributed to Teruki Kamon.

35 records · Page 2Linked to original sources

arXiv2014

Probing Light Nonthermal Dark Matter at the LHC

This paper investigates the collider phenomenolgy of a minimal nonthermal dark matter model with a 1-GeV dark matter candidate, which naturally explain baryongensis. Since the light dark matter is not parity-protected, it can be singly produced at the LHC. This leads to large missing energy associated with an energetic jet whose transverse momentum distribution is featured by a Jacobian-like shape. The monojet, dijet, paired dijet and 2 jets + missing energy channels are studied. Currently existing data at Tevatron and LHC offer significant bounds on our model.

hep-ph↗

arXiv2013

Probing Supersymmetric Dark Matter and the Electroweak Sector using Vector Boson Fusion Processes: A Snowmass Whitepaper

Vector boson fusion (VBF) processes at the Large Hadron Collider (LHC) provide a unique opportunity to search for new physics with electroweak couplings. Two studies are presented: (i) A search of supersymmetric dark matter in the final state of two VBF jets and large missing transverse energy is presented at 14 TeV. Prospects for determining the dark matter relic density are studied for the cases of Wino and Bino-Higgsino dark matter. The LHC could probe Wino dark matter with mass up to approximately 600 GeV with a luminosity of 1000 fb$^{-1}$. (ii) A search for the chargino/neutralino system in the final state of two VBF jets, missing transverse energy and two $τ$'s (light stau case) and light lepton $e$ and $μ$ (light slepton case). The $5 σ$ mass reach at 300 fb$^{-1}$ (1000 fb$^{-1}$) of LHC14 for inclusive and opposite-sign $τ$ pairs are 250 GeV (300 GeV) and 200 GeV (250 GeV), respectively, for $ΔM \, = \, m_{\tildeτ_1} - m_{\neu{1}} \, = \, 30$ GeV. For $ΔM \, = \, 15$ GeV, the $3 σ$ mass reach at 300 fb$^{-1}$ (1000 fb$^{-1}$) of LHC14 for inclusive $τ$ pairs is 180 GeV. The $5 σ$ mass reach at 300 fb$^{-1}$ (1000 fb$^{-1}$) of LHC14 for inclusive and opposite-sign $μ$ pairs are approximately 350 GeV (400 GeV) and 300 GeV (350 GeV), respectively. The mass reaches in the same-sign final state cases are similar to those in the opposite-sign cases.

hep-ph↗

arXiv2013

Probing Dark Matter at the LHC using Vector Boson Fusion Processes

Vector boson fusion (VBF) processes at the Large Hadron Collider (LHC) provide a unique opportunity to search for new physics with electroweak couplings. A feasibility study for the search of supersymmetric dark matter in the final state of two VBF jets and large missing transverse energy is presented at 14 TeV. Prospects for determining the dark matter relic density are studied for the cases of Wino and Bino-Higgsino dark matter. The LHC could probe Wino dark matter with mass up to approximately 600 GeV with a luminosity of 1000 fb$^{-1}$.

hep-ph↗

arXiv2013

Vector Boson Fusion Processes as a Probe of Supersymmetric Electroweak Sectors at the LHC

Vector boson fusion (VBF) processes offer a promising avenue to study the non-colored sectors of supersymmetric extensions of the Standard Model at the LHC. A feasibility study for searching for the chargino/neutralino system in the $R-$parity conserving Minimal Supersymmetric Standard Model is presented. The high $E_T$ forward jets in opposite hemispheres are utilized to trigger VBF events, so that the production of the lightest chargino and the second lightest neutralino can be probed without a bias by experimental triggers. Kinematic requirements are developed to search for signals of these supersymmetric states above Standard Model backgrounds in both $τ$ and light lepton ($e$ and $μ$) final states at $\sqrt{s} = 8$ TeV.

hep-ph↗

arXiv2012

Lepton Flavor Violation at the Large Hadron Collider

We investigate a potential of discovering lepton flavor violation (LFV) at the Large Hadron Collider. A sizeable LFV in low energy supersymmetry can be induced by massive right-handed neutrinos, which can explain neutrino oscillations via the seesaw mechanism. We investigate a scenario where the distribution of an invariant mass of two hadronically decaying taus ($\tauh\tauh$) from $\schizero{2}$ decays is the same in events with or without LFV. We first develop a transfer function using this ditau mass distribution to model the shape of the non-LFV $\tauhμ$ invariant mass. We then show the feasibility of extracting the LFV $\tauhμ$ signal. The proposed technique can also be applied for a LFV $\tauh e$ search.

hep-ph↗

arXiv2012

Searching for Top Squarks at the LHC in Fully Hadronic Final State

We pursue a scenario where the lighter top squark (stop) mass is accessible for the Large Hadron Collider (LHC) in the near future, while gluinos and first two generation squarks are heavier. At $\sqrt{s} = 8$ TeV, we investigate the identification of stops which decay predominantly into a top quark and the stable lightest supersymmetric particle. We use a simple kinematical variable, $M3$, to reconstruct two top quarks which are pair-produced from the stops, in the fully hadronic channel. The dominant Standard Model (SM) background for this signal stems from $t\bar t$ plus jets, with one top quark decaying into $ blν$, where the lepton is undetected and the $ν$ produces missing transverse momentum. The lepton identification efficiency is thus crucial in order to estimate the background correctly. We identify kinematical variables to reduce the SM background. We find that it is possible to achieve signal and background cross-section at similar levels for stop masses around $350 - 500$ GeV for a neutralino mass of 100 GeV.

hep-ph↗

arXiv2012

Diagnosis of Supersymmetry Breaking Mediation Schemes by Mass Reconstruction at the LHC

If supersymmetry is discovered at the LHC, the next question will be the determination of the underlying model. While this may be challenging or even intractable, a more optimistic question is whether we can understand the main contours of any particular paradigm of the mediation of supersymmetry breaking. The determination of superpartner masses through endpoint measurements of kinematic observables arising from cascade decays is a powerful diagnostic tool. In particular, the determination of the gaugino sector has the potential to discriminate between certain mediation schemes (not all schemes, and not between different UV realizations of a given scheme). We reconstruct gaugino masses, choosing a model where anomaly contributions to supersymmetry breaking are important (KKLT compactification), and find the gaugino unification scale. Moreover, reconstruction of other superpartner masses allows us to solve for the parameters defining the UV model. The analysis is performed in the stop and stau coannihilation regions where the lightest neutralinos are mainly gauginos, to additionally satisfy dark matter constraints. We thus develop observables to determine stau and stop masses to verify that the coannihilation mechanism is indeed operational, and solve for the relic density.

hep-ph↗

arXiv2011

Bi-Event Subtraction Technique at Hadron Colliders

We propose the Bi-Event Subtraction Technique (BEST) as a method of modeling and subtracting large portions of the combinatoric background during reconstruction of particle decay chains at hadron colliders. The combinatoric background arises when it is impossible to know experimentally which observed particles come from the decay chain of interest. The background shape can be modeled by combining observed particles from different collision events and be subtracted away, greatly reducing the overall background. This idea has been demonstrated in various experiments in the past. We generalize it by showing how to apply BEST multiple times in a row to fully reconstruct a cascade decay. We show the power of BEST with two simulated examples of its application towards reconstruction of the top quark and a supersymmetric decay chain at the Large Hadron Collider.

hep-ph↗

arXiv2010

Determination of Non-Universal Supergravity Models at the Large Hadron Collider

We examine a well motivated non-universal supergravity model where the Higgs boson masses are not unified with the other scalars at the grand unified scale at the LHC. The dark matter content can easily be satisfied in this model by having a larger Higgsino component in the lightest neutralino. Typical final states in such a scenario at the LHC involve W bosons. We develop a bi-event subtraction technique to remove a huge combinatorial background to identify W -> jj decays. This is also a key technique to reconstruct supersymmetric particle masses in order to determine the model parameters. With the model parameters, we find that the dark matter content of the universe can be determined in agreement with existing experimental results.

hep-ph↗

arXiv2009

Supersymmetry Signals of Supercritical String Cosmology at the Large Hadron Collider

We investigate the minimal supergravity (mSUGRA) signals at the LHC in the context of supercritical string cosmology (SSC). In this theory, the presence of a time dependent dilaton provides us with a smoothly evolving dark energy and modifies the dark matter allowed region of the mSUGRA model with standard cosmology. Such a dilaton dilutes the supersymmetric dark matter density (of neutralinos) by a factor O(10) and consequently the regions with too much dark matter in the standard scenario are allowed in the SSC. The final states expected at the LHC in this scenario, unlike the standard scenario, consist of Z bosons, Higgs bosons, and/or high energy taus. We show how to characterize these final states and determine the model parameters. Using these parameters, we determine the dark matter content and the neutralino-proton cross section. All these techniques can also be applied to determine model parameters in SSC models with different SUSY breaking scenarios.

hep-ph↗

arXiv2008

Determining the Dark Matter Relic Density in the Minimal Supergravity Stau-Neutralino Coannihilation Region at the Large Hadron Collider

We examine the stau-neutralino coannihilation (CA) mechanism of the early universe. We use the minimal supergravity (mSUGRA) model and show that from measurements at the Large Hadron Collider one can predict the dark matter relic density with an uncertainty of 6% with 30 fb-1 of data, which is comparable to the direct measurement by Wilkinson Microwave Anisotropy Probe. This is done by measuring four mSUGRA parameters m0, m1/2, A0 and tan(beta) without requiring direct measurements of the top squark and bottom squark masses. We also provide precision measurements of the gaugino, squark, and lighter stau masses in this CA region without assuming gaugino universality.

hep-ph↗

arXiv2007

Cosmology and Dark Matter at the LHC

We examine the question of whether neutralinos produced at the LHC can be shown to be the particles making up the astronomically observed dark matter. If the WIMP alllowed region lies in the SUGRA coannihilation region, then a strong signal for this would be the unexpected near degeneracy of the stau and neutralino i.e., a mass difference ΔM\simeq (5-15) GeV. For the mSUGRA model we show such a small mass difference can be measured at the LHC using the signal 3τ+jet+E_T^{\rm miss}. Two observables, opposite sign minus like sign pairs and the peak of the ττmass distribution allows the simultaneous determination of ΔM to 15% and the gluino mass M_{\tilde g} to be 6% at the benchmark point of M_{\tilde g}=850 GeV, A_0=0, μ>0 with 30 fb^{-1}. With 10 fb^{-1}, ΔM can be determined to 22% and one can probe the parameter space up to m_{1/2}=700 GeV with 100 fb^{-1}.

hep-ph↗

arXiv2006

Detection of SUSY in the Stau-Neutralino Coannihilation Region at the LHC

We study the feasibility of detecting the stau neutralino (stau_1-neutralino_1)coannihilation region at the LHC using tau leptons. The signal is characterized by multiple low energy tau leptons from neutralino_2-->tau stau_1-->tau tau neutralino_1 decays, where the stau_1 and neutralino_1 mass difference (Delta M) is constrained to be 5-15 GeV by current experimental bounds including the bound on the amount of neutralino cold dark matter. Within the framework of minimal supergravity models, we show that if hadronically decaying tau's can be identified with 50% efficiency for visible pt >20 GeV the observation of such signals is possible in the final state of two tau leptons plus large missing energy and two jets. With a gluino mass of 830 GeV the signal can be observed with as few as 3-10 fb^-1 of data (depending on the size of Delta M). Using a mass measurement of the tau pairs with 10 fb^-1 we can determine dM with a statistical uncertainty of 12% for Delta M = 10 GeV and an additional systematic uncertainty of 14% if the gluino mass has an uncertainty of 5%.

hep-ph↗

arXiv2005

The Stau Neutralino Co-annihilation Region at an International Linear Collider

We probe the stau-neutralino co-annihilation domain of the parameter space allowed by the current experimental bounds on the light Higgs mass, the b-> s γdecay, and the amount of neutralino cold dark matter within the framework of minimal SUGRA models at a 500 GeV e+e- linear collider. The most favorable signals of SUSY are stau pair production and neutralino pair production where the small mass difference between the lighter stau and the lightest neutralino in the co-annihilation region is ~5-15 GeV and hence generates low-energy tau leptons in the final state. This small mass difference would be a striking signal of many SUGRA models. We find that a calorimeter covering down to 1^o from the beams is crucial to reduce the two-photon background and the mass difference could be measured at a level of 10% with 500 fb^-1 of data where an invariant mass of two-tau jets and missing energy is used as a discriminator.

hep-ph↗

arXiv2005

Mass and Cross-section Measurements of Chargino at Linear Colliders in Large tan(beta) Case

The lighter chargino pair production ($e^+e^- \to \tildeχ^{+}_{1} \tildeχ^{-}_{1}$) is one of key processes for determination of supersymmetric parameters at a linear collider. If $\tanβ$ is a large value, the lighter stau ($\tildeτ^{\pm}_{1}$) might be lighter than the $\tildeχ^{\pm}_{1}$, while the other sleptons stay heavier. This case leads a cascade decay, $\tildeχ^{\pm}_{1} \to \tildeτ^{\pm}_{1} ν_τ$ followed by $\tildeτ^{\pm}_{1} \to \tildeχ^{0}_{1} τ^{\pm}$, where $\tildeχ^{0}_{1}$ is the lightest supersymmetric particle. This paper addresses to what extent this cascade decay may affect the measurements of the chargino mass and its production cross section.

hep-ph↗

arXiv1996

New Particle Searches at Tevatron (II)

Various recent results of new particle searches at the Fermilab Tevatron are presented. No evidence is found for supersymmetric particles (chargino, gluino), leptoquark bosons and heavy gauge bosons in p-pbar collisions at sqrt{s} = 1.8 TeV. Excluded mass regions for each particle are determined.

hep-ex↗