We explore the phenomenology of Kaluza-Klein (KK) dark matter in very general
models with universal extra dimensions (UEDs), emphasizing the complementarity
between high-energy colliders and dark matter direct detection experiments. In
models with relatively small mass splittings between the dark matter candidate
and the rest of the (colored) spectrum, the collider sensitivity is diminished,
but direct detection rates are enhanced. UEDs provide a natural framework for
such mass degeneracies. We consider both 5-dimensional and 6-dimensional
non-minimal UED models, and discuss the detection prospects for various KK dark
matter candidates: the KK photon $\gamma_1$, the KK $Z$-boson $Z_1$, the KK
Higgs boson $H_1$ and the spinless KK photon $\gamma_H$. We combine collider
limits such as electroweak precision data and expected LHC reach, with
cosmological constraints from WMAP, and the sensitivity of current or planned
direct detection experiments. Allowing for general mass splittings, we show
that neither colliders, nor direct detection experiments by themselves can
explore all of the relevant KK dark matter parameter space. Nevertheless, they
probe different parameter space regions, and the combination of the two types
of constraints can be quite powerful. For example, in the case of $\gamma_1$ in
5D UEDs the relevant parameter space will be almost completely covered by the
combined LHC and direct detection sensitivities expected in the near future.Comment: 52 pages, 29 figure

G. K. Mallot

Jonghee Yoo

Konstantin T. Matchev

Kyoungchul Kong

Laura Baudis

M. Carena

Sebastian Arrenberg

English

arXiv

We explore the phenomenology of Kaluza-Klein (KK) dark matter in very general models with universal extra dimensions (UEDs), emphasizing the complementarity between high-energy colliders and dark matter direct detection experiments. In models with relatively small mass splittings between the dark matter candidate and the rest of the (colored) spectrum, the collider sensitivity is diminished, but direct detection rates are enhanced. UEDs provide a natural framework for such mass degeneracies. We consider both five-dimensional and six-dimensional nonminimal UED models, and discuss the detection prospects for various KK dark matter candidates: the KK photon γ1, the KK Z boson Z1, the KK Higgs boson H1, and the spinless KK photon γH. We combine collider limits, such as electroweak precision data and expected LHC reach, with cosmological constraints from WMAP, and the sensitivity of current or planned direct detection experiments. Allowing for general mass splittings, we show that neither colliders nor direct detection experiments by themselves can explore all of the relevant KK dark matter parameter space. Nevertheless, they probe different parameter space regions, and the combination of the two types of constraints can be quite powerful. For example, in the case of γ1 in 5D UEDs the relevant parameter space will be almost completely covered by the combined CERN LHC and direct detection sensitivities expected in the near future

Arrenberg, S

Baudis, L

Kyoungchul, K

Matchev, K T

Yoo, J

ZORA

Kaluza-Klein dark matter: Direct detection vis-a-vis CERN LHC

We present updated results on the complementarity between high-energy colliders and dark matter direct detection experiments in the context of Universal Extra Dimensions (UED). In models with relatively small mass splittings between the dark matter candidate and the rest of the (colored) spectrum, the collider sensitivity is diminished, but direct detection rates are enhanced. UED provide a natural framework to study such mass degeneracies. We discuss the detection prospects for the KK photon γ 1 and the KK Z-boson Z 1 , combining the expected LHC reach with cosmological constraints from WMAP/Planck, and the sensitivity of current or planned direct detection experiments. Allowing for general mass splittings, neither colliders, nor direct detection experiments by themselves can explore all of the relevant KK dark matter parameter space. Nevertheless, they probe different parameter space regions, and the combination of the two types of constraints can be quite powerful. We present updated results on the complementarity between high-energy colliders and dark matter direct detection experiments  We take ∆ q 1 as a free parameter, which is possible in a more general framework with boundary terms and bulk masses (see, e.g.,  In the so defined (m LKP , ∆ q 1 ) parameter plane, in  [6] for 7+8 TeV). This signature results from the pair production (direct or indirect) arXiv:1307.6581v2 [hep-ph

Konstantin T Matchev

CiteSeerX

Kaluza-Klein Dark Matter: Direct Detection vis-a-vis LHC,”

Crossref

We explore the phenomenology of Kaluza-Klein (KK) dark matter in very general models with universal extra dimensions (UEDs), emphasizing the complementarity between high-energy colliders and dark matter direct detection experiments. In models with relatively small mass splittings between the dark matter candidate and the rest of the (colored) spectrum, the collider sensitivity is diminished, but direct detection rates are enhanced. UEDs provide a natural framework for such mass degeneracies. We consider both 5-dimensional and 6-dimensional non-minimal UED models, and discuss the detection prospects for various KK dark matter candidates: the KK photon {gamma}{sub 1} (5D) the KK Z-boson Z{sub 1} (5D) and the spinless KK photon {gamma}{sub H} (6D). We combine collider limits such as electroweak precision data and expected LHC reach, with cosmological constraints from WMAP and the sensitivity of current or planned direct detection experiments. Allowing for general mass splittings, we show that neither colliders, nor direct detection experiments by themselves can explore all of the relevant KK dark matter parameter space. Nevertheless, they probe different parameter space regions and the combination of the two types of constraints can be quite powerful. For example, in the case of {gamma}{sub 1} in 5D UEDs the relevant parameter space will be almost completely covered by the combined LHC and direct detection sensitivities expected in the near future

Arrenberg, Sebastian

Baudis, Laura

Kong, Kyoungchul

Matchev, Konstantin T.

Yoo, Jonghee

UNT (University of North Texas) Digital Library

arXiv:0811.4356v1  [hep-ph]  26 Nov 2008Kaluza-Klein Dark Matter: Direct Detection vis-a-visLHCSebastian Arrenberg∗a, Laura Baudisa, Kyoungchul Kongb, Konstantin T. Matchevcand Jonghee Yooba Physics Institute, University of Zürichb Fermi National Accelerator Laboratoryc Physics Department, University of FloridaE-mails: arrenberg@physik.uzh.ch, laura.baudis@physik.uzh.ch,kckong@fnal.gov, matchev@phys.ufl.edu, yoo@fnal.govWe explore the phenomenology of Kaluza-Klein (KK) dark matter in very general models withuniversal extra dimensions (UEDs), emphasizing the complementarity between high-energy col-liders and dark matter direct detection experiments. In models with relatively small mass splittingsbetween the dark matter candidate and the rest of the (colored) spectrum, the collider sensitivityis diminished, but direct detection rates are enhanced. UEDs provide a natural framework forsuch mass degeneracies. We consider both 5-dimensional and 6-dimensional non-minimal UEDmodels, and discuss the detection prospects for various KK dark matter candidates: the KK pho-ton γ1 (5D) the KK Z-boson Z1 (5D) and the spinless KK photon γH (6D). We combine colliderlimits such as electroweak precision data and expected LHC reach, with cosmological constraintsfrom WMAP and the sensitivity of current or planned direct detection experiments. Allowingfor general mass splittings, we show that neither colliders, nor direct detection experiments bythemselves can explore all of the relevant KK dark matter parameter space. Nevertheless, theyprobe different parameter space regions and the combination of the two types of constraints canbe quite powerful. For example, in the case of γ1 in 5D UEDs the relevant parameter space willbe almost completely covered by the combined LHC and direct detection sensitivities expected inthe near future. The work presented here is based on [1].Identification of dark matter 2008August 18-22, 2008Stockholm, Sweden∗Speaker.c© Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. http://pos.sissa.it/FERMILAB-CONF-08-591-TKaluza-Klein Dark Matter: Direct Detection vis-a-vis LHC Sebastian Arrenberg1. IntroductionIn the framework of UEDs [2] all standard model (SM) particles are promoted to one or moreflat, compactified extra dimensions. An infinite number of new particles, called Kaluza-Kleintower, arises for every SM particle. Since at tree level their masses receive a dominant contribution∼ TeV arising from the momentum carried along the extra dimension(s) the spectrum is highly de-generated and thus radiative corrections are significant. The lightest Kaluza-Klein partner (LKP) isstable and if it is neutral, it can be a possible dark matter candidate. Considering the mass spectrumwe did not restrict ourselves to the minimal UED (MUED) framework where vanishing boundaryinteractions at the cut-off scale are assumed, but rather allowed for a more general scenario takingthe mass splitting∆q1 =mq1 −mLKPmLKPbetween the LKP and the level one KK quarks as a free parameter.2. Relic density calculationsSince a high degree of mass degeneracy occurs quite naturally in models with UEDs it is ofparticular importance to take coannihilations into account when computing the relic density of theLKP candidate [3]. The procedure is straightforward. After all heavier particles have decayed intoit, the number density of the lightest species obeys a simple Boltzmann equation, where essentiallythe cross section has to be replaced by an effective cross section which depends on all annihilationcross sections and the mass splittings between the lightest particle and all other particles considered.We computed the relic densities for γ1 [3] and Z1 in 5D UED taking coannihilations with allother level one KK particles into account. In the MUED framework the γ1 is the LKP. The resultof the computation is shown as a dotted, red line in Fig. 1(a). In a second approach a certain masssplitting ∆ between the LKP and the KK quarks was assumed fixing the rest of the spectrum at theirFigure 1: Relic density of the LKP and constraints from electroweak precision data and WMAP.2Kaluza-Klein Dark Matter: Direct Detection vis-a-vis LHC Sebastian ArrenbergMUED masses. Each line in the plot is labeled with the corresponding value of ∆. Coannihilationsthus decrease the predictions for the relic density. In the case of the Z1 shown in Fig. 1(b) the quarkmasses were fixed in the same way as before. Z1 and W±1 are assumed to be degenerate while thegluon is heavier than Z1 by 10% and all other KK particles are heavier by 20%. In this case theeffect of coannihilations is inverted showing that its sign cannot easily be predicted. In both plotswe also show constraints from electroweak precision data [4, 5] as a cyan vertical band and thepreferred 2σ -WMAP region [6] as a green horizontal band. For example, a mass of 500 GeV forthe γ1 LKP in 5D MUED is a good benchmark.13. Direct LKP Detection - Predictions and LimitsIn order to explore constraints from direct detection experiments it is necessary to investigatethe elastic scattering between the dark matter particle and target nuclei. For all three LKP candi-dates considered here, γ1 and Z1 in 5D UED and γH in 6D UED, there are two Feynman diagramsarising from KK quark exchange and one from Higgs boson exchange, contributing to the scatteringcross section at tree level [1]. Here we only consider spin-independent scattering.The theoretical predictions are shown in Fig. 2. We fixed the Higgs mass at 120 GeV andassumed ∆ to be between 1% which is the upper boundary of the respective shaded area and 50%which is the lower boundary. The plot also contains cross section limits from CDMS [7] andXENON10 [8] as well as expected sensitivities from future experiments. Current experimentsalready exclude small mass splittings while future experiments should cover most of the relevantparameter space.Figure 2: Theoretical predictions for spin-independent LKP-nucleon cross sections and sensitivities fromcurrent and planned future direct detection experiments.1Note that the relic density including coannihilations of γH in 6D UED has not been investigated yet.3Kaluza-Klein Dark Matter: Direct Detection vis-a-vis LHC Sebastian Arrenberg4. Limits on Kaluza-Klein Dark MatterIn addition to calculating the limits on the spin-independent cross sections we also performeda more detailed analysis of the LKP specific parameter space.For example, one can translate the information from Fig. 2 into the ∆ vs. WIMP mass planewhen fixing the Higgs mass. This is shown in Fig. 3 for γ1 and Z1 in 5D UED. All mass splittingsbelow the respective limit curve are excluded. As expected direct detection experiments are par-ticularly sensitive to small ∆’s. Additionally both plots contain relic density constraints providingupper limits on the LKP mass. The black solid line accounts for all the dark matter in the universewhile the two black dotted lines show the bounds assuming that the LKP would contribute only1% or 10% to the total amount of dark matter. The green shaded region represents the preferred2σ -WMAP region [6]. For the case of the γ1 a collider study of the 4ℓ+ /ET channel yielded theresult that with a luminosity of 100 fb−1 the yellow shaded region should be covered by the LHC[9]. The LHC is thus more sensitive to large mass splittings. All three probes are highly comple-mentary and in the case of the γ1 the entire parameter space could be covered by ton-scale directdetection experiments.On the other hand, one can also interchange the role of the mass splitting and the Higgs mass.In Fig. 4 we show limits on the Higgs mass fixing ∆ at 10%. The excluded regions are below andto the left of each limit curve. The asymptotic behaviour is related to the decoupling of the Higgsexchange for large Higgs masses. In each plot the horizontal black line represents the current Higgsmass bound of 114 GeV while the diagonal line shows the limit from oblique corrections [5].2 Fromthe observation that the Higgs mass dependence in direct detection experiments only shows up inalready excluded parts of the parameter space it can be concluded that it plays a secondary roleinterpreting those experiments. Even future direct detection experiments will only probe a smallpart of the relevant parameter space, however the LHC will be more sensitive with respect to theHiggs mass.Figure 3: Limits from direct detection experiments, LHC studies and WMAP in the ∆ vs. mLKP plane.2Note that these corrections were computed considering the γ1 to be the LKP in MUED. Thus the correspondingbound in Fig. 4(b) has been included only for illustrative reasons.4Kaluza-Klein Dark Matter: Direct Detection vis-a-vis LHC Sebastian ArrenbergFigure 4: Limits from direct detection experiments and collider studies in the mh vs. mLKP plane.For a more detailed analysis, including the parameter space of γH LKP in 6D UED and spin-dependent interactions, we refer to [1].5. ConclusionWe performed a comprehensive phenomenological analysis of Kaluza-Klein dark matter, in-cluding constraints from direct detection experiments, collider studies and cosmology considering5D and 6D UED. It was shown that all three approaches are highly complementary and combiningthem substantially diminishes the relevant parameter space. Direct detection experiments restrictsmall values of ∆ whereas colliders are sensitive to large mass splittings. Cosmology on the otherhand rules out large LKP masses and as shown here these two parameters (∆ and mLKP) are the rel-evant quantities in analyzing UEDs. Moreover the importance of coannihilations for relic densitycomputations should be emphasized.Important investigations for the future in the context of UEDs would be further LHC and moredetailed relic density studies for certain LKP candidates such as the γH LKP in 6D UED.References[1] S. Arrenberg, L. Baudis, K. Kong, K.T. Matchev and J. Yoo, Phys. Rev. D 78, 056002 (2008)[hep-ph/0805.4210][2] D. Hooper and S. Profumo, Phys. Rept. 453, 29 (2007) [hep-ph/0701197][3] K. Kong and K.T. Matchev, JHEP 0601, 038 (2006) [hep-ph/0509119][4] T. Appelquist and H. U. Yee, Phys. Rev. D 67, 055002 (2003) [hep-ph/0211023][5] I. Gogoladze and C. Macesanu, Phys. Rev. D 74, 093012 (2006) [hep-ph/0605207][6] J. Dunkley et al. (WMAP Collaboration), [astro-ph/0803.0586][7] Z. Ahmed et al. (CDMS Collaboration), [astro-ph/0802.3530][8] J. Angle et al. (XENON10 Collaboration), Phys. Rev. Lett. 100, 021303 (2008)[astro-ph/0706.0039][9] H. C. Cheng, K.T. Matchev and M. Schmaltz, Phys. Rev. D 66, 056006 (2002) [hep-ph/0205314]5

Kaluza-Klein Dark Matter: Direct Detection vis-a-vis LHC

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