Discovery potential for supersymmetry at a high luminosity upgrade of LHC14

After completion of the LHC8 run in 2012, the plan is to upgrade the LHC for operation close to its design energy root s = 14 TeV, with a goal of collecting hundreds of fb(-1) of integrated luminosity. The time is propitious to begin thinking of what is gained by even further LHC upgrades. In this report, we compute an LHC14 reach for supersymmetry in the mSUGRA/CMSSM model with an anticipated high luminosity upgrade. We find that LHC14 with 300 (3000) fb(-1) has a reach for supersymmetry via gluino/squark searches of m((g) over tilde) similar to 3.2 TeV (3.6 TeV) for m((q) over tilde) similar to m((g) over tilde), and a reach of m((g) over tilde) similar to 1.8 TeV (2.3 TeV) for m((q) over tilde) >> m((g) over tilde). In the case where m((q) over tilde) >> m((g) over tilde), then the LHC14 reach for chargino-neutralino production with decay into the Wh + 6 is not an element of(T) final state reaches to m((g) over tilde) similar to 2.6 TeV for 3000 fb(-1).

Wh plus missing-E-T signature from gaugino pair production at the LHC

In SUSY models with heavy squarks and gaugino mass unification, the gaugino pair production reaction pp -> (W) over tilde (+/-)(1)(Z) over tilde (2) dominates gluino pair production for m (g) over tilde less than or similar to 1 TeV at LHC with root s = 14 TeV (LHC14). For this mass range, the two-body decays (W) over tilde (1) -> W (Z) over tilde (1) and (Z) over tilde (2) -> h (Z) over tilde (1) are expected to dominate the chargino and neutralino branching fractions. By searching for lb (b) over tilde + is not an element of(T) events from (W) over tilde (+/-)(1)Z(2) production, we show that LHC14 with 100 fb(-1) of integrated luminosity becomes sensitive to chargino masses in the range m((W) over tilde1) similar to 450-550 GeV corresponding to m (g) over tilde similar to 1.5-2 TeV in models with gaugino mass unification. For 10(3) fb(-1), LHC14 is sensitive to the Wh channel for m((W) over tilde1) similar to 300-800 GeV, corresponding to m (g) over tilde similar to 1-2.8 TeV, which is comparable to the reach for gluino pair production followed by cascade decays. The Wh + is not an element of(T) search channel opens up a new complementary avenue for SUSY searches at LHC, and serves to point to SUSYas the origin of any new physics discovered via multijet and multilepton + is not an element of(T) channels.

W Z plus missing-E-T signal from gaugino pair production at LHC7

LHC searches for supersymmetry currently focus on strongly produced sparticles, which are copiously produced if gluinos and squarks have masses of a few hundred GeV. However, in supersymmetric models with heavy scalars, as favored by the decoupling solution to the SUSY flavor and CP problems, and m((g) over tilde) greater than or similar to 500 GeV as indicated by recent LHC results, chargino-neutralino ((W) over tilde (+/-)(1)(Z) over tilde (2)) production is the dominant cross section for m((W) over tilde1) similar to m((Z) over tilde2) < m(<(g)over tilde>)/3 at LHC with root s = 7 TeV (LHC7). Furthermore, if m((Z) over tilde1) + (m (Z) over tilde) less than or similar to m((Z) over tilde2) less than or similar to m((Z) over tilde1) + m(h), then (Z) over tilde (2) dominantly decays via (Z) over tilde (2) -> (Z) over tilde (1)Z, while (W) over tilde (1) decays via (W) over tilde (1) -> (Z) over tilde W-1. We investigate the LHC7 reach in the W Z + (sic)T channel (for both leptonic and hadronic decays of the W boson) in models with and without the assumption of gaugino mass universality. In the case of the mSUGRA/CMSSM model with heavy squark masses, the LHC7 discovery reach in the W Z+ (sic)T channel becomes competetive with the reach in the canonical (sic)T + jets channel for integrated luminosities similar to 30 fb(-1). We also present the LHC7 reach for a simplified model with arbitrary m((Z) over tilde1) and m((W) over tilde1) similar to m((Z) over tilde2). Here, we find a reach of up to m((W) over tilde1) similar to 200 (250) GeV for 10 (30) fb(-1).

LHC discovery potential for supersymmetry with root s=7 TeV and 5-30 fb(-1)

We extend our earlier results delineating the supersymmetry reach of the CERN Large Hadron Collider operating at a center-of-mass energy root s = 7 TeV to integrated luminosities in the range 5-30 fb(-1). Our results are presented within the paradigm minimal supergravity model or constrained minimal supersymmetric standard model. Using a six-dimensional grid of cuts for the optimization of signal to background ratio-including missing E-T-we find for m((g) over tilde) similar to m((q) over tilde) an LHC 5 sigma supersymmetry discovery reach of m((g) over tilde) similar to 1:3, 1.4, 1.5, and 1.6 TeV for 5, 10, 20, and 30 fb(-1), respectively. For m((q) over tilde) >> m((g) over tilde), the corresponding reach is instead m((g) over tilde) similar to 0: 8, 0.9, 1.0, and 1.05 TeV, for the same integrated luminosities.

Wgamma production and limits on anomalous WWgamma couplings in ppbar collisions

We measure the cross section and the difference in rapidities between photons and charged leptons for inclusive W -> lnu+gamma production in egamma and mugamma final states. Using data corresponding to an integrated luminosity of 4.2 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider, the cross section multiplied by the branching fraction for the process ppbar -> Wgamma+X -> lnugamma+X, measured to be 15.8 +/- 0.8 (stat.) +/- 1.2 (syst.) pb, and the distribution of the charge-signed photon-lepton rapidity difference are found to be in agreement with the standard model. These results provide the most stringent limits on anomalous WWgamma couplings for data from hadron colliders: -0.4 < Delta kappa_gamma < 0.4 and -0.08 < lambda_gamma < 0.07 at the 95% C.L.

Indications of Conical Emission of Charged Hadrons at the BNL Relativistic Heavy Ion Collider

Three-particle azimuthal correlation measurements with a high transverse momentum trigger particle are reported for pp, d + Au, and Au + Au collisions at root(S)NN = 200 GeV by the STAR experiment. Dijet structures are observed in pp, d + Au and peripheral Au + Au collisions. An additional structure is observed in central Au + Au data, signaling conical emission of correlated charged hadrons. The conical emission angle is found to be theta = 1.37 +/- 0.02(stat)(-0.07)(+0.06)(syst), independent of p perpendicular to.

System-Size Independence of Directed Flow Measured at the BNL Relativistic Heavy-Ion Collider

We measure directed flow (v(1)) for charged particles in Au + Au and Cu + Cu collisions at root s(NN) = 200 and 62.4 GeV, as a function of pseudorapidity (eta), transverse momentum (p(t)), and collision centrality, based on data from the STAR experiment. We find that the directed flow depends on the incident energy but, contrary to all available model implementations, not on the size of the colliding system at a given centrality. We extend the validity of the limiting fragmentation concept to v(1) in different collision systems, and investigate possible explanations for the observed sign change in v(1)(p(t)).

Probing neutrino oscillations in supersymmetric models at the Large Hadron Collider

The lightest supersymmetric particle may decay with branching ratios that correlate with neutrino oscillation parameters. In this case the CERN Large Hadron Collider (LHC) has the potential to probe the atmospheric neutrino mixing angle with sensitivity competitive to its low-energy determination by underground experiments. Under realistic detection assumptions, we identify the necessary conditions for the experiments at CERN's LHC to probe the simplest scenario for neutrino masses induced by minimal supergravity with bilinear R parity violation.

Quirky collider signals of folded supersymmetry

We investigate the collider signals associated with scalar quirks (squirks) in folded supersymmetric models. As opposed to regular superpartners in supersymmetric models these particles are uncolored, but are instead charged under a new confining group, leading to radically different collider signals. Because of the new strong dynamics, squirks that are pair produced do not hadronize separately, but rather form a highly excited bound state. The excited squirkonium loses energy to radiation before annihilating back into standard model particles. We calculate the branching fractions into various channels for this process, which is prompt on collider time scales. The most promising annihilation channel for discovery is W+photon which dominates for squirkonium near its ground state. We demonstrate the feasibility of the LHC search, showing that the mass peak is visible above the SM continuum background and estimate the discovery reach.

Hadronic resonance production in d+Au collisions at root S(NN) = 200 GeV measured at the BNL Relativistic Heavy Ion Collider

We present the first measurements of the rho(770)(0),K(*)(892),Delta(1232)(++),Sigma(1385), and Lambda(1520) resonances in d+Au collisions at s(NN)=200 GeV, reconstructed via their hadronic decay channels using the STAR detector (the solenoidal tracker at the BNL Relativistic Heavy Ion Collider). The masses and widths of these resonances are studied as a function of transverse momentum p(T). We observe that the resonance spectra follow a generalized scaling law with the transverse mass m(T). The < p(T)> of resonances in minimum bias collisions are compared with the < p(T)> of pi,K, and p. The rho(0)/pi(-),K(*)/K(-),Delta(++)/p,Sigma(1385)/Lambda, and Lambda(1520)/Lambda ratios in d+Au collisions are compared with the measurements in minimum bias p+p interactions, where we observe that both measurements are comparable. The nuclear modification factors (R(dAu)) of the rho(0),K(*), and Sigma(*) scale with the number of binary collisions (N(bin)) for p(T)> 1.2 GeV/c.

Probing wrong-sign Yukawa couplings at the LHC and a future linear collider

We consider the two-Higgs-doublet model as a framework in which to evaluate the viability of scenarios in which the sign of the coupling of the observed Higgs boson to down-type fermions (in particular, b-quark pairs) is opposite to that of the Standard Model (SM), while at the same time all other tree-level couplings are close to the SM values. We show that, whereas such a scenario is consistent with current LHC observations, both future running at the LHC and a future e(+)e(-) linear collider could determine the sign of the Higgs coupling to b-quark pairs. Discrimination is possible for two reasons. First, the interference between the b-quark and the t-quark loop contributions to the ggh coupling changes sign. Second, the charged-Higgs loop contribution to the gamma gamma h coupling is large and fairly constant up to the largest charged-Higgs mass allowed by tree-level unitarity bounds when the b-quark Yukawa coupling has the opposite sign from that of the SM (the change in sign of the interference terms between the b-quark loop and the W and t loops having negligible impact).

ATLAS Run 1 searches for direct pair production of third-generation squarks at the Large Hadron Collider

This paper reviews and extends searches for the direct pair production of the scalar supersymmetric partners of the top and bottom quarks in proton--proton collisions collected by the ATLAS collaboration during the LHC Run 1. Most of the analyses use 20 fb−1 of collisions at a centre-of-mass energy of s√=8 TeV, although in some case an additional 4.7 fb−1 of collision data at s√=7 TeV are used. New analyses are introduced to improve the sensitivity to specific regions of the model parameter space. Since no evidence of third-generation squarks is found, exclusion limits are derived by combining several analyses and are presented in both a simplified model framework, assuming simple decay chains, as well as within the context of more elaborate phenomenological supersymmetric models.

Limits on Anomalous Couplings from Higgs Boson Production at the Fermilab Tevatron Collider

We estimate the attainable limits on the coefficients of dimension-6 operators from the analysis of Higgs boson phenomenology, in the framework of a SUL(2)UY(1) gauge-invariant effective Lagrangian. Our results, based on the data sample already collected by the collaborations at Fermilab Tevatron, show that the coefficients of Higgs-vector boson couplings can be determined with unprecedented accuracy. Assuming that the coefficients of all blind operators are of the same magnitude, we are also able to impose more restrictive bounds on the anomalous vector-boson triple couplings than the present limit from double gauge boson production at the Tevatron collider.