Searching for New Spin Dependent Macroscopic Forces Using Two Particle Exchange

7 .22 .08

INDIANA UNIVERSITY 8

Marks: Block IU and IUPUI

I d en t i t y C omponen t s

BLOCK IU

A diverse assortment of graphic representations of “IU,” Indiana University’s acronym, has been in use dating back to 1898. Many variations appear in limestone carvings throughout the university, and many more have been developed for other applications.

One version of the IU expression, created and first implemented in 2002, and referred to as the Block IU, has been selected as the foundational element for the Indiana University Integrated Image Program. It is graphically strong, simple, communicative, and can be quite effective when integrated with other elements.

The IU Seal, discussed in detail later in this guide, is to be reserved for ceremonial and executive-level communications. Given that many universities have institutional seals of approximately the same contours, the Block IU offers a more differentiating presentation. IU has also been represented in the past by a wordmark; however, while distinctive, it does not provide the flexibility to accommodate the complex identification system required by the university’s various needs and has therefore been discontinued.

Adopting the Block IU as the standard across all media and increasing its presence will help meet the objectives of the program and provide synergies supporting the extensive presence of the university throughout the state and world.

IUPU I WORDMARK

Because the Indiana University–Purdue University Indianapolis campus is a partnership between Indiana and Purdue Universities, the Block IU is not an appropriate mark to represent that campus. An IUPUI wordmark in the official IU Font proudly showcases both school colors.

S. Aldaihan1, W. M. Snow1, D. Krause2, J. C. Long1

1Indiana University ,Department of Physics, Bloomington, Indiana,47408.2Wabash College, Department of Physics,Crawfordsville,Indriana,47933.

Forces existing in nature: 1.  Electromagnetic force 2.  Weak nuclear force.3.  Strong nuclear force.4.  Gravitational force5.  Fifth force ≈ [1μm,1mm]

Why a New Force?

Current Limits on g and λ

dark energy density corresponds to a length scale encourages search for new phenomena at this scale in particular.

(1meV )4

≈100µm

The mass and the strength of coupling is unknown but general parameterizations of forces mediated by light

particles can be derived based on all allowed couplings between matter (fermions) and force carriers (bosons)

Spin dependent couplings are weaker by at least 10 orders of magnitude!

coupling constant, is approximately K < 4 ⇥ 10�18 s/kg. This is about two orders of magnitudeless sensitive than the experiment in [39], which used a SQUID magnetometer to monitor theinteraction between spin-polarized test masses and a paramagnetic salt. However, the scale of thetest masses in that experiment and their separation were on the order of 5 cm. The sensitivity ofthe proposed short-range spin-dependent experiment to the full expression in Eq. 4 is still beingevaluated.

Figure 1: Left: Parameter space for proposed cryogenic experiment in which the strength ↵ (relativeto gravity) of a new force is plotted versus the range �. Right: Parameter space for proposed spin-dependent experiment. In each plot, the experimentally excluded region is above and to the right ofthe solid, bold curves. Fine and dotted lines are theoretical predictions. Bold dashed lines indicatethe ultimate, practical sensitivity of the proposed experiments

3 Theoretical Predictions

Despite its enormous success, there is widespread impression that the standard model of particlephysics (SM) is incomplete. It provides neither su�cient explanation of particle masses nor of theobserved matter-antimatter asymmetry of the universe. It does not include gravity, and appearsincompatible with general relativity. Extensions to the SM, including those attempting to incor-porate gravity and particle physics in the same theoretical framework, predict many new particlesor even contain extra spacetime dimensions, both of which phenomena can manifest in new e↵ectsbelow 1 mm. Comprehensive reviews are given in [24], [1], and [2]; below is a brief description ofsome of the testable predictions.

String theory, the leading candidate for a unified description of gravity and particle physics, hasto be formulated in more than three spatial dimensions. The theory contains scalar fields calledmoduli and dilatons that parameterize the extra dimensions and the string coupling. These fieldscan acquire mass in the meV range via a variety of symmetry-breaking scenarios, and are thuspredicted to mediate forces according to Eq. 1 in the sub-mm range with a wide range of couplings[3, 13, 16, 15, 30, 9] (Fig. 1, left). In a major development in the 1990s, models were discovered inwhich unification can occur at a scale much lower than the presumed Planck scale (⇠ 1016 TeV)

3

r is the distance between the fermionsm is the mass of the fermionλ is the proposed Compton wavelength of the boson.gs is the scalar coupling constant. gp is the pseudoscalar coupling constant and is always accompanied by the fermion spin operator σ .

Concept of the SearchLimits from Two Particles Exchange using IU Spin Independent

Experiment searching for New Macroscopic Forces

One Particle vs. Two Particle Exchange in Spin dependent interactions

⎪⎭

⎪⎬

⎫Standard Model Spin flip after

one interaction

Original spin direction is

restored after two interactions

⎪⎩

⎪⎨

⎧Spin dependent couplings

16 possible forms of interactions

θ

(a)

(b)

θ1

θ2

We calculated forces arising from two particle exchange and Found the leading effects to have the following functional forms

K1(x) is the modified Bessel function of the second kind

Applicable in the limit Which is satisfied with a large safety margin in macroscopic experiments