Resolving the existence of Higgsinos in the LHC inverse problem

The LHC inverse problem is infamously challenging when neutralinos and charginos are heavy and pure and other superparticles are decoupled. This limit is becoming more relevant to particle physics nowadays. Fortunately, in this limit, Higgsinos produce a distinctive signature if they are the LSPs or NLSPs. The identifying signature is the presence of equal numbers of Z bosons and Higgs bosons in NLSP productions and subsequent decays at hadron colliders. The signature is derived from the Goldstone equivalence theorem by which partial widths into Z and Higgs bosons are inherently related and from the fact that Higgsinos consist of two indistinguishable neutralinos. Thus it is valid in general for many supersymmetry models; exceptions may happen when Higgsino NLSPs decay to weakly coupled LSPs such as axinos or gravitinos.Comment: 25 pages, 6 figures; v.2: published version with measurement prospects update

Probing Light Stops with Stoponium

We derive new limits on light stops from diboson resonance searches in the $\gamma\gamma$, $Z \gamma$, $ZZ$, $WW$ and $hh$ channels from the first run of the LHC. If the two-body decays of the light stop are mildly suppressed or kinematically forbidden, stoponium bound states will form in $pp$ collisions and subsequently decay via the pair annihilation of the constituent stops to diboson final states, yielding striking resonance signatures. Remarkably, we find that stoponium searches are highly complementary to direct collider searches and indirect probes of light stops such as Higgs coupling measurements. Using an empirical quarkonia potential model and including the first two $S$-wave stoponium states, we find that in the decoupling limit $m_{\widetilde t_1} \lesssim 130$ GeV is excluded for any value of the stop mixing angle and heavy stop mass by the combination of the latest resonance searches and the indirect constraints. The $\gamma \gamma$ searches are the most complementary to the indirect constraints, probing the stop "blind spot" parameter region in which the $h^0 \tilde t_1 \tilde t_1^*$ trilinear coupling is small. Interestingly, we also find that the $Z\gamma$ searches give a stronger constraint, $m_{\widetilde t_1} \lesssim 170$ GeV, if the stop is primarily left-handed. For a scenario with a bino LSP and stop NLSP, several gaps in the direct collider searches for stops can unambiguously be filled with the next run of the LHC. For a stop LSP decaying through an R-parity violating $UDD$ coupling, the stoponium searches can fill the gap 100 GeV $\lesssim m_{\tilde t_1} \lesssim 200$ GeV in the direct searches for couplings $\lambda" \lesssim 10^{-2}$.Comment: 35 pages, 33 figures. v2: references adde

Gravitational-Wave Fringes at LIGO: Detecting Compact Dark Matter by Gravitational Lensing

Utilizing gravitational-wave (GW) lensing opens a new way to understand the small-scale structure of the universe. We show that, in spite of its coarse angular resolution and short duration of observation, LIGO can detect the GW lensing induced by compact structures, in particular by compact dark matter (DM) or primordial black holes of $10 - 10^5 \, M_\odot$, which remain interesting DM candidates. The lensing is detected through GW frequency chirping, creating the natural and rapid change of lensing patterns: \emph{frequency-dependent amplification and modulation} of GW waveforms. As a highest-frequency GW detector, LIGO is a unique GW lab to probe such light compact DM. With the design sensitivity of Advanced LIGO, one-year observation by three detectors can optimistically constrain the compact DM density fraction $f_{\rm DM}$ to the level of a few percent.Comment: 6 pages, 5 figures, v2: published version, Fig.5 updated with Poisson distribution, improved discussion on the optical dept

Constraining Higgsino Kink Tracks from Existing LHC Searches

Considering the supersymmetric model with the long-lived charged Higgsino, we discuss how Higgsino kink signals can show up in the latest LHC Disappearing Track (DT) and stable chargino searches. We derive constraints on the Higgsino kink signal, and characterize it in comparison to the Wino DT and the slepton kink track. We also discuss how to infer Higgsino model kinematics.Comment: 5 pages, 6 figures. v3: published version with major update based on the latest dat