Detectability of the second resonance of low-scale string models at the LHC

Abstract

Low-scale string models are phenomenological models in String Theory, in which the string scale M s is of the order of TeV. String excited states which are characteristic modes in low-scale string models can be observed as resonances in dijet invariant mass distributions at the LHC. If a new heavy resonance is discovered at the LHC, it is important to investigate whether the resonance comes from low-scale string models. In this work, two analyses are performed: One is observing higher spin degeneracy of string excited states by an angular distribution analysis on the resonance, since the string resonance consists of several degenerate states with different spins. The other is observing second string excited states by a search for a second resonance in dijet invariant mass distributions, since second string excited states have characteristic masses of √ 2 times of masses of first string excited states. As the result of Monte Carlo simulations assuming the 14 TeV LHC, we give required luminosities for 5 σ confirmation in each analysis, in case of M s = 4.5, 4.75 and 5 TeV.1 It is pointed out in Ref.[8], for example, that light string excited states are possible even with a high string scale due to the warp effect in the Randall-Sundrum scenario.2 The Wigner d-function d J Jz,J z ′ (θ) represents an angular dependence of a process through a state with spin J, in which an initial state has total spin along z-axis, J z , and a final state has total spin along z ′ -axis, J z ′ . The angle θ is that between the z-axis and z ′ -axis.

Production of light stringy states

“…[24][25][26][27][28][29][30]), or purely stringy signatures (see, e.g. [31][32][33][34][35][36][37][38][39][40][41][42][43][44]). 3 Such a scenario is displayed in figure 1, where the Standard Model sector is localized on a small region of the full Calabi-Yau manifold.…”

Yukawas of light stringy states (at D-brane intersections)

“…A key feature of these vacua is that the string scale can be very low, even at a few TeV range [26][27][28], and stringy effects become possible candidates for physics beyond the Standard Model (see for example anomalous Z [29][30][31][32][33][34][35][36][37][38][39][40][41][42], Kaluza Klein states [43][44][45][46][47][48][49], or purely stringy signatures [50][51][52][53][54][55][56][57][58][59][60][61][62][63] 3 ).…”

Yukawa couplings for light stringy states

“…A novel property of this class of models is that the string scale can be significantly low, even at a few TeV range [26][27][28]. Therefore, stringy effects become viable candidates for physics beyond the Standard Model (see or example anomalous Z [29][30][31][32][33][34][35][36][37][38][39][40][41][42], Kaluza Klein states [43][44][45][46][47][48][49], or purely stringy signatures [50][51][52][53][54][55][56][57][58][59][60][61][62][63] 3 .…”