# Sho's catennel

## Physics —Papers (Activities)—

### Graduation Work (2008) "Linear Collider —to-> Relic Density"

The work I did in the "Undergraduate Research"   course; this work was supervised by Dr. Masako Iwasaki, a lecturer of Aihara Lab. (lab on experimental particle physics).

We followed the work by Feng and Peskin, and showed how precisely we can measure the mass of the superpaticles with the International Linear Collider.

This report is written in Japanese.

Related talk: 30 Mar. 2008 Generation-86 Graduation Work Exhibition slides

### Magisterial Thesis (2010) "Supersymmetry without R-Parity: Its Phenomenology"

The magisterial thesis, mainly focused on my previous work; supervised by Prof. Koichi Hamaguchi.

We in this paper reviewed the R-parity violation, symmetries imposed instead of the R-parity, and experimental constraints on the R-parity violating couplings; then we, as done in the previous work, but more pedagogically, discuss cosmological constraints on the couplings which become severe in the presence of lepton flavor violation.

We investigate in detail the R-parity violating SUSY, especially the constraints on its parameters. The constraints are mainly obtained from collider experiments, and they are of order 10-3-10-4. However, we found that, if lepton ﬂavor violating processes are strong enough to equilibrate the lepton ﬂavor asymmetry in the early universe, which is naturally expected in various models, the present baryon–antibaryon asymmetry brings us much more stringent constraints of order 10-6-10-7.

(Older versions: 2010.02.08[v1]2010.03.06[v2])

Related talk: 01 Feb. 2010 Defense for Master's Degree slides

### Dissertation (2013) "Supersymmetry after Higgs discovery and its LHC phenomenology"

TBW

The current status of the supersymmetric theories is described in this dissertation. First, the simplest model of supersymmetric Standard Model is introduced, which is called the MSSM. Under this framework, the discrepancy in the muon anomalous magnetic moment between the prediction from the Standard Model and the experimental result suggests the supersymmetric particles are of order 100 GeV, which is also supported by discussions on the little hierarchy problem. However, the LHC experiments have found no scalar-quarks or gluinos in such mass range, and moreover, the Higgs boson mass of 126\,GeV requires, within the MSSM framework, the scalar-top mass of order 1 to 10 TeV. This current status forces us to abandon the simplest supersymmetry-breaking frameworks of the CMSSM and the GMSB scenarios.

Two promising possibilities remain there: the first is that the scalar-quarks and the gluino are much heavier than of order 100 GeV while the other SUSY particles remain near the order, and the second is to extend the MSSM with extra fields. The second scenario is investigated in this dissertation; the V-MSSM is proposed as an extension of the MSSM with a ($$\vc{10}+\overline{\vc{10}}$$) pair of the SU(5) decuplets. In the framework the Higgs mass is increased by effect from the extra matters, and thus the 126 GeV is achieved with the scalar-top having a lighter mass. This fact resurrects the CMSSM and the GMSB scenarios. This dissertation examines the GMSB scenario under the V-MSSM; it is called V-GMSB scenario.

It is shown that the V-GMSB has a potential to realize the 126 GeV mass of the Higgs boson with holding the explanation of the muon magnetic moment discrepancy, if the masses of the extra quarks are approximately less than 1.2 TeV. Constraints on the V-GMSB from the LHC experiments are discussed then; it is concluded that the gluino mass must be approximately heavier than 1.1 TeV, and that the extra quarks be heavier than 300 to 650 GeV depending on the decay branches of them.

### Lepton Flavor Violation and Cosmological Constraints on R-parity Violation

In this paper we discussed the cosmological constraints on the R-parity violation. You can find more pedagogical discussion in my magisterial thesis, Section 3 and 4; it would be a great help if you are new to this topic, although it is not so sophisticated as that in this paper...

In supersymmetric standard models R-parity violating couplings are severely constrained, since otherwise they would erase the existing baryon asymmetry before the electroweak transition. It is often claimed that this cosmological constraint can be circumvented if the baryon number and one of the lepton flavor numbers are sufficiently conserved in these R-parity violating couplings, because $$B/3-L_i$$ for each lepton flavor is separately conserved by the sphaleron process. We discuss the effect of lepton flavor violation on the $$B-L$$ conservation, and show that even tiny slepton mixing angles $$\theta_{12} \gtrsim {\mathcal O}(10^{-4})$$ and $$\theta_{23}, \theta_{13}\gtrsim {\mathcal O}(10^{-5})$$ will spoil the separate $$B/3-L_i$$ conservation. In particular, if lepton flavor violations are observed in experiments such as MEG and B-factories, it will imply that all the R-parity violating couplings must be suppressed to avoid the $$B-L$$ erasure. We also discuss the implication for the decay of the lightest MSSM particle at the LHC.

Authors: Motoi Endo, Koichi Hamaguchi, and Sho Iwamoto

Paper: JCAP 1002 (2010) 032 (2010)

Related talk: 20 Feb. 2010 KEK-PH 2010 slides

Related talk: 04 Oct. 2010 2nd Bethe Center Workshop slides

### Stau Kinks at the LHC

In this paper is discussed "kink tracks", an exotic signature detected by the TRT (ATLAS/LHC). Especially we discuss stau kink tracks, focusing on the following two models: (1) SUSY with a stau MSSM-LSP, R-parity violated in $$LL\bar E$$ or $$LH\s u$$; (2) SUSY with a gravitino LSP, a stau NLSP. Roughly speaking, if $$\lambda\sim 10^{-7}\,\text{--}\,10^{-10}$$ in (1), or if $$m_{3/2}\sim 10^{-2}\,\text{--}\,10\un{keV}$$ in (2), we would be achieve discovery of such kink signatures with 14TeV LHC.

I want to emphasize two points. The one is that this approach is very effective to find long-lived staus ($$c\tau\sim \mathcal O(\un{m})$$). The other is that the reach of (1) is the favored region with respect to the discussion in my previous paper.

We investigate the possibility of probing SUSY models by analyzing the kink signatures of charged tracks at the LHC. As underlying models, we consider two models, SUSY models with a gravitino LSP and a stau NLSP, and R-parity violating SUSY models with a stau (N)LSP. We show that, if the decay length is $$\mathcal O(10\,\text{--}\,10^5)\un{mm}$$, a large number of kink events can be discovered in a wide range of the SUSY parameters. We also discuss model discrimination by identifying the daughter particles of the kink tracks.

Authors: Shoji Asai, Yuya Azuma, Motoi Endo, Koichi Hamaguchi, and Sho Iwamoto

Paper: JHEP 1112 (2011) 041 (2011)

Related talk: 20 Aug. 2011 YONUPA Summer School 2011 slides

Related talk: 07 Sep. 2011 IPMU–YITP School on Monte Carlo Tools for LHC poster

Related talk: 16 Jan. 2012 Universität Bonn slides

Related talk: 30 Jan. 2012 DESY slides

Related talk: 27 Feb. 2012 KEK-PH 2012 slides

### Higgs Mass and Muon Anomalous Magnetic Moment in Supersymmetric Models with Vector-Like Matters

We had, in 2012 summer, some 2 sigma indication of 130-140 GeV Higgs. It was extremely heavier than expected, and if we assume the MSSM framework, such mass cannot be achieved without very very fine tuning, which was of a great depression. This depression stands out with taking the muon g-2 anomaly into consideration, which requires a much lighter SUSY scale.

So we extend the MSSM with $$\vc{10}+\overline{\vc{10}}$$, or extra vector-like quarks. Such extra matters yields $$y'Q'H\s u\bar U'$$ coupling, which drastically lifts up the Higgs mass with the same mechanism as $$y_t$$, and with the help we can keep the SUSY scale lighter to achieve the SUSY explanation of the muon $$g-2$$ anomaly.

The 130-140 GeV Higgs signal disappeared soon, actually died at a few months, as is usual for 2-sigma excesses, but this framework was used in the next paper.

We study the muon anomalous magnetic moment (muon $$g-2$$) and the Higgs boson mass in a simple extension of the minimal SUSY Standard Model with extra vector-like matters, in the frameworks of GMSB models and mSUGRA models. It is shown that the deviation of the muon $$g-2$$ and a relatively heavy Higgs boson can be simultaneously explained in large $$\tan\beta$$ region. (i) In GMSB models, the Higgs mass can be more than 135 GeV (130 GeV) in the region where muon $$g-2$$ is consistent with the experimental value at the $$2\sigma$$ ($$1\sigma$$) level, while maintaining the perturbative coupling unification. (ii) In the case of mSUGRA models with universal soft masses, the Higgs mass can be as large as about 130 GeV when muon $$g-2$$ is consistent with the experimental value at the $$2\sigma$$ level. In both cases, the Higgs mass can be above 140 GeV if the $$g-2$$ constraint is not imposed.

Authors: Motoi Endo, Koichi Hamaguchi, Sho Iwamoto, and Norimi Yokozaki

Paper: Phys. Rev. D 84 (2011) 075017 (2011)

Related paper: a successive work on LHC Phenomenology

Related paper: a successive work on vacuum stability

Related talk: 18 Feb. 2012 Physics opportunities with LHC at 7 TeV slides

Related talk: 20 Feb. 2012 Winter Toyama 2012, phenomenology & cosmology workshop slides

Related talk: 09 Mar. 2012 Sapporo Winter School 2012 slides

Related talk: 15 Mar. 2012 GUT2012 slides

Related talk: 19 Apr. 2012 Niigata University and University of Toyama slides

### LHC Dijet Signals in New Physics Models for Top Forward-Backward Asymmetry

It is shown that the flavor changing $$Z'$$ model, which can be explain the anomalies in the top forward-backward asymmetry, gives a signature on the dijet ($$pp\to{\rm jj}$$) measurement in the LHC experiment.

This means the LHC experiment would give another clue than the charge asymmetry to explore the origin of the anomaly, which is quite important in this era where the Tevatron unfortunately shut down.

Actually I have done many analyses besides shown in this letter, which I would give in some talks :)

The dijet signature at the LHC is studied in new physics models for the top forward-backward asymmetry at the Tevatron. In the $$t$$-mediator models, flavor-changing interactions contribute to the dijet production cross section as well as the asymmetry at least at the one-loop level. It is found that the LHC dijet measurements at $$36\un{pb}^{-1}$$ have constrained the $$Z'$$ coupling larger than 2.5-3. The sensitivity is expected to be improved significantly as the integrated luminosity increases in the LHC.

Authors: Motoi Endo and Sho Iwamoto

Paper:

Related talk: 13 Aug. 2011 SI2011 (phenomenology)

### Higgs mass, muon g-2, and LHC prospects in gauge mediation models with vector-like matters

The 130-140 GeV Higgs died soon, but after a few months we found excesses of $$\sim 3\sigma$$ around 125 GeV.

Even for 125 GeV, it is difficult to realize the simultaneous explanation of the Higgs mass and the muon $$g-2$$ anomaly. It can be achieved with setting the gluino mass heavier than the bino/wino mass, or setting the 3rd-generation scalar mass heavier than the 1st and 2nd generation mass, at the GUT scale. It is somewhat peculiar for us, and thus we dug up the previous framework which we proposed for 130-140 GeV Higgs. It allows us to achieve the simultaneous explanation within the framework of the GMSB and the CMSSM.

We also discuss LHC prospects; SUSY searches and 4th generation quark searches. The SUSY searches give lower bounds on the SUSY scale (depending on the signature, or the MSSM-LSP and its lifetime) even with a dataset corresponds to $$1\text{--}2{\rm fb^{-1}}$$. The 4th generation searches have yielded no general bound because the extra vector-like matters have several decay branch, but assuming the decay products several mass bounds can be obtained; here we would like to emphasize the importance of the search for $$t'\to th\to bWb\bar b$$ signature.

Recently the ATLAS and CMS collaborations presented preliminary results of Standard Model Higgs searches and reported excesses of events for a Higgs boson at 124-126 GeV. Such a Higgs mass can be naturally realized, simultaneously explaining the muon $$g-2$$ anomaly, in gauge-mediated SUSY breaking models with extra vector-like matters. Upper bounds are obtained on the gluino mass, $$m_{\tilde g}\lesssim 1.2\ (1.8)\,\rm TeV$$, and on the extra vector-like quark mass, $$M_{Q'}\lesssim 1.0\ (1.8)\,\rm TeV$$, in the parameter region where the Higgs boson mass is 124-126 GeV and the muon $$g-2$$ is consistent with the experimental value at the $$1\sigma\ (2\sigma)$$ level. The LHC prospects are explored in the parameter region. It is found that some of the regions are already excluded by the LHC, and most of the parameter space is expected to be covered at $$\sqrt s=14\,\rm TeV$$ A study on the extra vector-like quarks, especially current bounds on their masses and prospects for future searches, is also included.

Authors: Motoi Endo, Koichi Hamaguchi, Sho Iwamoto, and Norimi Yokozaki

Paper: Phys. Rev. D 85 (2012) 095012 (2012)

Related paper: a successive work on vacuum stability

Related talk: 18 Feb. 2012 Physics opportunities with LHC at 7 TeV slides

Related talk: 20 Feb. 2012 Winter Toyama 2012, phenomenology & cosmology workshop slides

Related talk: 09 Mar. 2012 Sapporo Winter School 2012 slides

Related talk: 15 Mar. 2012 GUT2012 slides

Related talk: 19 Apr. 2012 Niigata University and University of Toyama slides

Related talk: 06 Aug. 2012 YONUPA Summer School 2012 slides

Related talk: 15 Jan. 2013 Dissertation Defense slides

Related talk: 08 Feb. 2013 Kyushu University slides

Related talk: 01 May 2013 Kavli IPMU slides

### mass and muon anomalous magnetic moment in the U(1) extended MSSM

This work is, similar to the previous work a study on a model which can realize the simultaneous explanation of the Higgs mass and the muon $$g-2$$ anomaly. In this paper we extend the MSSM with an extra U(1) gauge symmetry.

We first see that the simultaneous realization is certainly achieved, and then LHC phenomenology is discussed.

We study phenomenological aspects of the MSSM with extra U(1) gauge symmetry. We find that the lightest Higgs boson mass can be increased up to 125 GeV, without introducing a large SUSY scale or large A-terms, in the frameworks of the CMSSM and gauge mediated SUSY breaking (GMSB) models. This scenario can simultaneously explain the discrepancy of the muon anomalous magnetic moment (muon $$g-2$$) at the 1σ level, in both of the frameworks, U(1)-extended CMSSM/GMSB models. In the CMSSM case, the dark matter abundance can also be explained.

Authors: Motoi Endo, Koichi Hamaguchi, Kazunori Nakayama, Sho Iwamoto, and Norimi Yokozaki

Paper: Phys. Rev. D 85 (2012) 095006 (2012)

Related talk: 19 Apr. 2012 Niigata University and University of Toyama slides

### Vacuum Stability Bound on Extended GMSB Models

TBW

Extensions of GMSB models were recently explored to explain the recent reports of the Higgs boson mass around 124-126 GeV. Some models predict a large $$\mu$$ term, which can spoil the vacuum stability of the universe. We study two GMSB extensions: i) the model with a large trilinear coupling of the top squark, and ii) that with extra vector-like matters. In both models, the vacuum stability condition provides upper bounds on the gluino mass if combined with the muon $$g-2$$. The whole parameter region is expected to be covered by LHC at $$\sqrt s =14\,\rm TeV$$. The analysis is also applied to the mSUGRA models with the vector-like matters.

Authors: Motoi Endo, Koichi Hamaguchi, Sho Iwamoto, and Norimi Yokozaki

Paper: JHEP 1206 (2012) 060 (2012)

Related paper: a previous work on LHC Phenomenology

### Muon g-2 anomaly and 125 GeV Higgs : Extra vector-like quark and LHC prospects

This article is written for the proceedings of the conference GUT2012 held at Kyoto University in March. The content is based on the slides together with a bit more discussions on searches for the extra vector-like particles. For more detailed discussions, please refer our previous papers [1108.3701] [1112.5653] [1202.2751].

The ATLAS and CMS collaborations recently reported indication of a Higgs boson around 125 GeV. If we add extra vector-like quarks to the MSSM, such a relatively heavy Higgs can be naturally realized in the GMSB framework, simultaneously explaining the muon $$g-2$$ anomaly. I will discuss LHC prospects of this attractive model.

Authors: Sho Iwamoto

Paper: AIP Conf. Proc. 1467 (2012) 57‒61 (2012)

Related talk: 15 Mar. 2012 GUT2012 slides

Related talk: 19 Apr. 2012 Niigata University and University of Toyama slides

Related talk: 06 Aug. 2012 YONUPA Summer School 2012 slides

Related talk: 15 Jan. 2013 Dissertation Defense slides

Related talk: 08 Feb. 2013 Kyushu University slides

Related talk: 01 May 2013 Kavli IPMU slides

### Comment on the CMS search for charge-asymmetric production of W' boson in ttbar + jet events

This article contains comments on a recent paper [1206.3921] by the CMS collaboration, where an inclusive search for new physics in $$pp\to t\bar tj$$ events. This search targets an extra $$W'$$ boson which couples to the top and down quarks, which motivated by the Tevatron top forward-backward asymmetry.

We first tried to interpret their results on $$M_{W'}\text{--}g_{\rm R}$$ plane, but our calculated cross section does not match theirs, and we consider this possibility. This is a very short paper with 7 pages; especially the text is just for 3 pages. We wrote up this article in 3 days. Actually the PC spent more time on the calculation than I spent on the writing...

A reanalysis is presented on the CMS result on a search for a $$W'$$ boson that couples to the top and down quarks. The model is motivated by the Tevatron results on the forward-backward asymmetry of $$t\bar t$$ pair production. In the evaluation of the theoretical cross section of $$pp\to t\bar tj$$, the interference effect between the SM and $$W'$$ amplitudes is shown to be important, though it is ignored in the CMS analysis. The lower mass bound on the $$W'$$ boson is relaxed from 840 GeV to 740 GeV at the 95% C.L. due to the interference effect. The bound is also compared to the top forward-backward asymmetry.

Authors: Motoi Endo and Sho Iwamoto

Paper: Phys. Lett. B 718 (2013) 1070‒1072 (2013)

### Gauge Mediation Models with Vectorlike Matters at the LHC

Constraints from LHC SUSY searches on the model in our previous work is discussed in this paper. The model is very attractive because it simultaneously realizes the 126 GeV Higgs boson, observed in July 2012, and the discrepancy on the muon anomalous magnetic moment between the experimental result and theoretical prediction without modifying SUSY-breaking mechanism, i.e., even under the minimal GMSB scenario.

Note that the LSP in this model is the gravitino. We conclude that, if the gaugino is the NLSP, the gaugino with its mass of $$m_{\tilde g}\lesssim1.1{\,\rm TeV}$$ is excluded under this model, with interpreting recent SUSY searches at the LHC.

Furthermore, as long as the NLSP does not decay promptly, we found that the gaugino must be heavier than 1.1 TeV even if it is not the NLSP, and also that the extra vector-like quark should be less than $$\sim1.1{\,\rm TeV}$$, which is certainly within the reach of the 14 TeV LHC.

Gauge mediation model with vectorlike matters (V-GMSB) is one of the few viable SUSY models that explains the 126 GeV Higgs boson mass and the muon anomalous magnetic moment simultaneously. We explore exclusion bounds on V-GMSB model from latest LHC SUSY searches.

Authors: Motoi Endo, Koichi Hamaguchi, Kazuya Ishikawa, Sho Iwamoto, and Norimi Yokozaki

Paper: JHEP 1301 (2013) 181 (2013)

Related paper: a previous work on LHC Phenomenology

Related paper: a previous work on vacuum stability

### Muon g-2 vs LHC in Supersymmetric Models

There is more than 3σ deviation between the experimental and theoretical results of the muon $$g-2$$. This suggests that some of the SUSY particles have a mass of order 100 GeV. We study searches for those particles at the LHC with particular attention to the muon $$g-2$$. In particular, the recent results on the searches for the non-colored SUSY particles are investigated in the parameter region where the muon $$g-2$$ is explained. The analysis is independent of details of the SUSY models. Future prospects of the collider searches are also discussed.

Authors: Motoi Endo, Koichi Hamaguchi, Sho Iwamoto, and Takahiro Yoshinaga

Paper: JHEP 1401 (2014) 123 (2014)

Related talk: 08 Feb. 2013 Kyushu University slides

Related talk: 13 Feb. 2013 HPNP2013 slides

Related talk: 01 May 2013 Kavli IPMU slides

Related talk: 27 Aug. 2013 SUSY 2013 slides

Related talk: 07 Dec. 2013 ATLAS-Japan workshop slides

Related talk: 17 Dec. 2014 Joint particle physics meeting (Tel Aviv U.) slides

### Recent Result of the AMS-02 Experiment and Decaying Gravitino Dark Matter in Gauge Mediation

The AMS-02 collaboration has recently reported an excess of cosmic-ray positron fractions, which is consistent with previous results at PAMELA and Fermi-LAT experiments. The result indicates the existence of new physics phenomena to provide the origin of the energetic cosmic-ray positron. We pursue the possibility that the enhancement of the positron fraction is due to the decay of gravitino dark matter. We discuss that such a scenario viably fits into the models in which the soft SUSY breaking parameters are dominantly from gauge-mediation mechanism with superparticle masses of around 10 TeV. Our scenario is compatible with 126 GeV Higgs boson, negative searches for SUSY particles, and non-observation of anomalous flavor-changing processes. We also point out that the scenario will be tested in near future by measuring the electric dipole moment of the electron and the lepton flavor violating decay of the muon.

Authors: Masahiro Ibe, Sho Iwamoto, Shigeki Matsumoto, Takeo Moroi, and Norimi Yokozaki

Paper: JHEP 1308 (2013) 029 (2013)

Related talk: 20 Nov. 2013 PASCOS 2013 slides

### Reconstructing Supersymmetric Contribution to Muon Anomalous Magnetic Dipole Moment at ILC

We study the possibility to determine the supersymmetric (SUSY) contribution to the muon anomalous magnetic dipole moment by using ILC measurements of the properties of superparticles. Assuming that the contribution is as large as the current discrepancy between the result of the Brookhaven E821 experiment and the standard-model prediction, we discuss how and how accurately the SUSY contribution can be reconstructed. We will show that, in a sample point, the reconstruction can be performed with the accuracy of $$\sim13\%$$ with the center-of-mass energy 500 GeV and the integrated luminosity $$\sim500$$-$$1000{\rm\,fb^{-1}}$$.

Authors: Motoi Endo, Koichi Hamaguchi, Sho Iwamoto, Teppei Kitahara, and Takeo Moroi

Paper: Phys. Lett. B 728 (2014) 274‒281 (2014)

Related talk: 13 Feb. 2014 BURI 2014 slides

Related talk: 21 Jul. 2014 ILC Summer Camp 2014 slides

Related talk: 22 Jul. 2014 ILC Summer Camp 2014 slides

### CP-safe Gravity Mediation and Muon g-2

SUSY is a good candidate to solve the discrepancy of muon $$g-2$$ between the experimental result and theoretical expectations. To this end, non-colored SUSY particles should be as light as O(100) GeV, while the Higgs boson mass suggests colored SUSY particles should be heavier than 1 TeV. This separation can be explained by non-universal gaugino mass, which though involves the risk of CP-violation because of phase misalignments among the gaugino masses. To solve this problem, we built a model which has no CP-violation to realize the non-universal gaugino mass.

This work was in collaboration with Tsutomu and Norimi; we were heading back from the cafeteria and talking the model to solve the anomaly; I was interested in gaugino mediation and told Tsutomu it was good, but he realized that CP-violation which the model involves is critically bad. Then we stop thinking, but a day Tsutomu suddenly came with a model. Norimi and I analyzed the model, and confirmed that the model fits to my purpose to solve the anomaly.

We propose a CP-safe gravity mediation model, where the phases of the Higgs B parameter, scalar trilinear couplings and gaugino mass parameters are all aligned. Since all dangerous CP violating phases are suppressed, we are now safe to consider low-energy SUSY scenarios. As an application, we consider a gravity mediation model explaining the observed muon $$g-2$$ anomaly. The CP-safe property originates in two simple assumptions: SUSY breaking in the Kähler potential and a shift symmetry of a SUSY breaking field $$Z$$. As a result of the shift symmetry, the imaginary part of $$Z$$ behaves as a QCD axion, leading to an intriguing possibility: the strong CP problem in QCD and the SUSY CP problem are solved simultaneously.

Authors: Sho Iwamoto, Tsutomu T. Yanagida, and Norimi Yokozaki

Paper: PTEP 2015 073B01 (2015)

Related talk: 30 Jul. 2014 Progress of Particle Physics 2014 slides

Related talk: 25 Aug. 2014 SI2014 (phenomenology) slides

Related talk: 17 Dec. 2014 Joint particle physics meeting (Tel Aviv U.) slides

### Long-Lived Sleptons at the LHC and a 100 TeV Proton Collider

This work shows how far we can search for long-lived charged particles in future colliders. To answer this question is, actually, not very interesting; just do Monte Carlo simulation, and that's all. However, in this work, we realized two features at the future collider as important; one is the radiative energy loss of muons, which can only be seen in such high energy, and the other is the fact that we should carefully treat the momentum resolution in such high energy.

This work was originated in May 2014; I thought I could finish before long, but as our Monte Carlo simulation as well as statistical treatment was done very seriously, and the manuscript writing was with much argument, it finally took one year. (and also, as actually the biggest reason, because I moved from Japan to Israel in this period.)

We study the prospects for long-lived charged particle (LLCP) searches at current and future LHC runs and at a 100 TeV pp collider, using Drell-Yan slepton pair production as an example. Because momentum measurements become more challenging for very energetic particles, we carefully treat the expected momentum resolution. At the same time, a novel feature of 100 TeV collisions is the significant energy loss of energetic muons in detectors. We use this to help discriminate between muons and LLCPs. We find that the 14 TeV LHC with an integrated luminosity of $$3\,{\rm ab^{-1}}$$ can probe LLCP slepton masses up to 1.2 TeV, and a 100 TeV pp collider with $$3\,{\rm ab^{-1}}$$ can probe LLCP slepton masses up to 4 TeV, using time-of-flight measurements. These searches will have striking implications for dark matter, with the LHC definitively testing the possibility of slepton-neutralino co-annihilating WIMP dark matter, and with the LHC and future hadron colliders having a strong potential for discovering LLCPs in models with superWIMP dark matter.

Authors: Jonathan L. Feng, Sho Iwamoto, Yael Shadmi, and Shlomit Tarem

Paper: JHEP 1512 (2015) 166 (2015)

Related talk: 24 Aug. 2015 SUSY 2015 slides