Search for a high-mass diphoton state and limits on Randall-Sundrum gravitons at CDF Page: 4 of 10
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to UNT Digital Library by the UNT Libraries Government Documents Department.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
4
the Fermilab Tevatron. We find the diphoton mass spectrum to be in agreement with the standard
model expectation, and set limits on the cross section times branching ratio for the Randall-Sundrum
graviton, as a function of diphoton mass. We subsequently derive lower limits for the graviton mass
of 230 GeV/c2 and 850 GeV/c2, at the 95% confidence level, for coupling parameters (k/MP) of
0.01 and 0.1 respectively.
PACS numbers: 12.38.Qk 13.85.Rm 13.85.QkA potential signature for new, heavy particles is
a narrow mass resonance decaying to two energetic
photons. Such a signature could arise from extra
spatial dimensions, as in the Randall-Sundrum (RS)
model [1]. In this Letter we present the results of the
search for this signature in pp collision data from the
CDF II Detector at the Fermilab Tevatron.
Some string theories propose that as many as
seven new spatial dimensions may exist, with their
geometry potentially responsible for the apparent
weakness of gravity (the hierarchy problem). In
the minimal RS model, this geometry is a five-
dimensional space with negative curvature, bounded
by two three-dimensional, spatially extended mem-
branes (or brandss'). These branes are separated by
a distance 7rrc, where r, is the compactification ra-
dius. Using 0 as the coordinate of the extra dimen-
sion (0 0 < 7r), the standard model (SM) particles
are confined to the "TeV" brane, located at 0 = 7r,
while the gravitational wavefunction is localized at
0 = 0. The scale of physical phenomena on the
TeV brane is specified by A, = Mml e-krr, where
Mr; = Mpl/ = 2.4 x 1018 GeV is the effective
four-dimensional (reduced) Planck scale and k is a
curvature parameter of the order of the Planck scale.
To remove the hierarchy between gravity and
the electroweak force, A, is set to approximately
1 TeV. The Planck scale then arises from the small
overlap of the graviton wave function with the TeV
brane in the fifth dimension, and the compactifi-
cation scale gives rise to a Kaluza Klein tower of
*With visitors from 'University of Athens, 15784 Athens,
Greece, bUniversity of Bristol, Bristol BS8 1TL, United King-
dom, CUniversity Libre de Bruxelles, B-1050 Brussels, Bel-
gium, dCornell University, Ithaca, NY 14853, 'University
of Cyprus, Nicosia CY-1678, Cyprus, fUniversity College
Dublin, Dublin 4, Ireland, 9University of Edinburgh, Edin-
burgh EH9 3JZ, United Kingdom, hUniversity of Heidelberg,
D-69120 Heidelberg, Germany, tUniversidad Iberoamericana,
Mexico D.F., Mexico, 'University of Manchester, Manchester
M13 9PL, England, kNagasaki Institute of Applied Science,
Nagasaki, Japan, 'University de Oviedo, E-33007 Oviedo,
Spain, 'University of London, Queen Mary College, Lon-
don, E1 4NS, England, 'University of California Santa Cruz,
Santa Cruz, CA 95064, 'Texas Tech University, Lubbock, TX
79409, PUniversity of California, Irvine, Irvine, CA 92697,
4IFIC(CSIC-Universitat de Valencia), 46071 Valencia, Spain,graviton states, an infinite set of four-dimensional
particles with increasing masses. This mass spec-
trum is given by m, = x,(k/Mpj)A,, where x,, are
the roots of the first-order Bessel function, and the
states couple with strength 1/A,. Thus, the widths
and masses of the resonances are dependent on the
parameter k/MmI.
The values of k must be large enough to be con-
sistent with the apparent weakness of gravity, but
small enough to prevent the theory from becoming
non-perturbative [2]. Given these considerations, we
examine values in the range 0.01 < k/MmP < 0.1.
For this range, graviton production results in a
diphoton mass peak narrower than the CDF detector
resolution. The spin-2 nature of the graviton, decay-
ing by either s- or p-wave states, favors searches in
the diphoton channel, where the branching ratio is
twice that of any single dilepton channel.
Existing lower mass limits on RS gravitons
from a search using the DO detector, in the com-
bined diphoton, dielectron, and dimuon channels,
are 250 GeV/c2 for k/MPj = 0.01 and 785 GeV/c2
for k/MPj = 0.1 at the 95% confidence level
(C.L.) [3]. The previous limits from the CDF collab-
oration are from a combined dielectron and dimuon
search, with limits of 170 GeV/c2 and 710 GeV/c2
for k/Mml = 0.01 and 0.1 respectively [4].
This search uses 1.2 fb- of integrated luminos-
ity collected by the CDF II Detector operating at
= 1.96 TeV. The detector [5] is approximately
forward-backward and azimuthally symmetric. A
seven-layer (eight-layer in the forward region) sili-
con tracker [6] is surrounded by an open-cell drift
chamber (COT) [7]. The fiducial coverage of the
COT is i77 < 1.0, and the silicon detector extends
the tracking coverage to ij7 < 2.0. The integrated
tracking system is contained within a superconduct-
ing solenoid, providing a 1.4 T magnetic field. Sur-
rounding these are the electromagnetic and hadronic
calorimeters [8], divided into "central" (177 < 1.1)
and "plug" (1.1 < 177 < 3.6) regions, providing mea-
surements of both shower energy and position. At
the approximate electromagnetic shower maximum,
the calorimeters contain fine-grained detectors [9]
that measure the shower shape and centroid posi-
tion in the two dimensions transverse to the shower
Upcoming Pages
Here’s what’s next.
Search Inside
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Aaltonen, T.; Abulencia, A.; Adelman, J.; Affolder, Anthony Allen; Akimoto, T.; Albrow, Michael G. et al. Search for a high-mass diphoton state and limits on Randall-Sundrum gravitons at CDF, article, July 1, 2007; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc880710/m1/4/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.